Enable LCID marshalling and clean up our LCID marshalling tests. (#24642)

* Enable LCID marshalling and clean up our LCID marshalling tests.

* Fix return type.

* Enable LCID IDispatch reverse marshalling

* Add more tests for LCID marshalling.

* Add testing for reverse-IDispatch. Fix bug in Thread::GetCulture when culture has not been initialized on the managed side.

* PR Feedback.

* Fix install command.

24 files changed, 683 insertions, 305 deletions

diff --git a/src/vm/dllimport.cpp b/src/vm/dllimport.cpp
index 7fc0863a6c..469a06e887 100644
--- a/src/vm/dllimport.cpp
+++ b/src/vm/dllimport.cpp
@@ -451,8 +451,7 @@ public:
         STANDARD_VM_CONTRACT;
 
         ILCodeStream* pcs = m_slIL.GetDispatchCodeStream();
-        
-#ifdef FEATURE_USE_LCID
+
         if (SF_IsReverseStub(m_dwStubFlags))
         {
             if ((m_slIL.GetStubTargetCallingConv() & IMAGE_CEE_CS_CALLCONV_HASTHIS) == IMAGE_CEE_CS_CALLCONV_HASTHIS)
@@ -504,12 +503,6 @@ public:
                 pcs->EmitCALL(METHOD__CULTURE_INFO__GET_ID, 1, 1);
             }
         }
-#else // FEATURE_USE_LCID
-        if (SF_IsForwardStub(m_dwStubFlags))
-        {
-            pcs->EmitLDC(0x0409); // LCID_ENGLISH_US
-        }
-#endif // FEATURE_USE_LCID
 
         // add the extra arg to the unmanaged signature
         LocalDesc locDescNative(ELEMENT_TYPE_I4);
diff --git a/src/vm/interoputil.cpp b/src/vm/interoputil.cpp
index c516a27eef..a6eab2280e 100644
--- a/src/vm/interoputil.cpp
+++ b/src/vm/interoputil.cpp
@@ -984,7 +984,6 @@ void GetCultureInfoForLCID(LCID lcid, OBJECTREF *pCultureObj)
     }
     CONTRACTL_END;
 
-#ifdef FEATURE_USE_LCID
     OBJECTREF CultureObj = NULL;
     GCPROTECT_BEGIN(CultureObj)
     {
@@ -1004,9 +1003,6 @@ void GetCultureInfoForLCID(LCID lcid, OBJECTREF *pCultureObj)
         *pCultureObj = CultureObj;
     }
     GCPROTECT_END();
-#else
-    COMPlusThrow(kNotSupportedException);
-#endif
 }
 
 #endif // CROSSGEN_COMPILE
diff --git a/src/vm/mscorlib.h b/src/vm/mscorlib.h
index 50188f0407..d328d2a471 100644
--- a/src/vm/mscorlib.h
+++ b/src/vm/mscorlib.h
@@ -272,10 +272,8 @@ DEFINE_CLASS(CULTURE_INFO,          Globalization,          CultureInfo)
 DEFINE_METHOD(CULTURE_INFO,         STR_CTOR,               .ctor,                      IM_Str_RetVoid)
 DEFINE_FIELD(CULTURE_INFO,          CURRENT_CULTURE,        s_userDefaultCulture)
 DEFINE_PROPERTY(CULTURE_INFO,       NAME,                   Name,                       Str)
-#ifdef FEATURE_USE_LCID
 DEFINE_METHOD(CULTURE_INFO,         INT_CTOR,               .ctor,                      IM_Int_RetVoid)
 DEFINE_PROPERTY(CULTURE_INFO,       ID,                     LCID,                       Int)
-#endif
 DEFINE_FIELD(CULTURE_INFO,          CULTURE,                s_currentThreadCulture)
 DEFINE_FIELD(CULTURE_INFO,          UI_CULTURE,             s_currentThreadUICulture)
 DEFINE_STATIC_SET_PROPERTY(CULTURE_INFO, CURRENT_CULTURE,      CurrentCulture,     CultureInfo)
diff --git a/src/vm/threads.cpp b/src/vm/threads.cpp
index 7632bda555..945cb3a601 100644
--- a/src/vm/threads.cpp
+++ b/src/vm/threads.cpp
@@ -7918,8 +7918,6 @@ OBJECTREF Thread::GetCulture(BOOL bUICulture)
     }
     CONTRACTL_END;
 
-    FieldDesc *         pFD;
-
     // This is the case when we're building mscorlib and haven't yet created
     // the system assembly.
     if (SystemDomain::System()->SystemAssembly()==NULL || g_fForbidEnterEE) {
@@ -7927,22 +7925,9 @@ OBJECTREF Thread::GetCulture(BOOL bUICulture)
     }
 
     OBJECTREF pCurrentCulture;
-    if (bUICulture) {
-        // Call the Getter for the CurrentUICulture.  This will cause it to populate the field.
-        MethodDescCallSite propGet(METHOD__CULTURE_INFO__GET_CURRENT_UI_CULTURE);
-        ARG_SLOT retVal = propGet.Call_RetArgSlot(NULL);
-        pCurrentCulture = ArgSlotToObj(retVal);
-    } else {
-        //This is  faster than calling the property, because this is what the call does anyway.
-        pFD = MscorlibBinder::GetField(FIELD__CULTURE_INFO__CURRENT_CULTURE);
-        _ASSERTE(pFD);
-
-        pFD->CheckRunClassInitThrowing();
-
-        pCurrentCulture = pFD->GetStaticOBJECTREF();
-        _ASSERTE(pCurrentCulture!=NULL);
-    }
-
+    MethodDescCallSite propGet(bUICulture ? METHOD__CULTURE_INFO__GET_CURRENT_UI_CULTURE : METHOD__CULTURE_INFO__GET_CURRENT_CULTURE);
+    ARG_SLOT retVal = propGet.Call_RetArgSlot(NULL);
+    pCurrentCulture = ArgSlotToObj(retVal);
     return pCurrentCulture;
 }
 
diff --git a/tests/src/Common/Platform/platformdefines.h b/tests/src/Common/Platform/platformdefines.h
index 5f051185f9..c501264aa4 100644
--- a/tests/src/Common/Platform/platformdefines.h
+++ b/tests/src/Common/Platform/platformdefines.h
@@ -148,7 +148,8 @@ typedef int error_t;
 typedef void* LPVOID;
 typedef unsigned char BYTE;
 typedef WCHAR OLECHAR;
-typedef double DATE;
+typedef double DATE;          
+typedef DWORD LCID;
 #endif
 
 typedef ULONG_PTR DWORD_PTR;
diff --git a/tests/src/Interop/CMakeLists.txt b/tests/src/Interop/CMakeLists.txt
index aa19c68002..b8dc69c31c 100644
--- a/tests/src/Interop/CMakeLists.txt
+++ b/tests/src/Interop/CMakeLists.txt
@@ -83,6 +83,7 @@ if(WIN32)
     add_subdirectory(COM/NativeClients/Primitives)
     add_subdirectory(COM/NativeClients/Licensing)
     add_subdirectory(COM/NativeClients/DefaultInterfaces)
+    add_subdirectory(COM/NativeClients/Dispatch)
     add_subdirectory(WinRT/NativeComponent)
 
     # IJW isn't supported on ARM64
diff --git a/tests/src/Interop/COM/NETClients/IDispatch/Program.cs b/tests/src/Interop/COM/NETClients/IDispatch/Program.cs
index ad44b300d0..d658bff2c3 100644
--- a/tests/src/Interop/COM/NETClients/IDispatch/Program.cs
+++ b/tests/src/Interop/COM/NETClients/IDispatch/Program.cs
@@ -5,6 +5,7 @@
 namespace NetClient
 {
     using System;
+    using System.Globalization;
     using System.Reflection;
     using System.Runtime.InteropServices;
 
@@ -151,6 +152,24 @@ namespace NetClient
             Assert.Throws<NotSupportedException>(() => dispatchTesting.DoubleHVAValues(ref input));
         }
 
+        static void Validate_LCID_Marshaled()
+        {
+            var dispatchTesting = (DispatchTesting)new DispatchTestingClass();
+            CultureInfo oldCulture = CultureInfo.CurrentCulture;
+            CultureInfo newCulture = new CultureInfo("es-ES", false);
+            try
+            {
+                CultureInfo englishCulture = new CultureInfo("en-US", false);
+                CultureInfo.CurrentCulture = newCulture;
+                int lcid = dispatchTesting.PassThroughLCID();
+                Assert.AreEqual(englishCulture.LCID, lcid);  // CLR->Dispatch LCID marshalling is explicitly hardcoded to en-US instead of passing the current culture.
+            }
+            finally
+            {
+                CultureInfo.CurrentCulture = oldCulture;
+            }
+        }
+
         static int Main(string[] doNotUse)
         {
             // RegFree COM is not supported on Windows Nano
@@ -166,6 +185,7 @@ namespace NetClient
                 Validate_Double_In_ReturnAndUpdateByRef();
                 Validate_Exception();
                 Validate_StructNotSupported();
+                Validate_LCID_Marshaled();
             }
             catch (Exception e)
             {
diff --git a/tests/src/Interop/COM/NETClients/Primitives/StringTests.cs b/tests/src/Interop/COM/NETClients/Primitives/StringTests.cs
index 0c1212ceae..5b2bc4bed5 100644
--- a/tests/src/Interop/COM/NETClients/Primitives/StringTests.cs
+++ b/tests/src/Interop/COM/NETClients/Primitives/StringTests.cs
@@ -6,6 +6,7 @@ namespace NetClient
 {
     using System;
     using System.Collections.Generic;
+    using System.Globalization;
     using System.Linq;
     using System.Text;
     using System.Runtime.InteropServices;
@@ -54,6 +55,7 @@ namespace NetClient
             this.Marshal_LPString();
             this.Marshal_LPWString();
             this.Marshal_BStrString();
+            this.Marshal_LCID();
         }
 
         static private string Reverse(string s)
@@ -267,5 +269,32 @@ namespace NetClient
                 Assert.AreEqual(local, actual);
             }
         }
+
+        private void Marshal_LCID()
+        {
+            Console.WriteLine("Marshal LCID");
+            foreach (var s in reversableStrings)
+            {
+                string local = s;
+                string expected = Reverse(local);
+
+                string actual = this.server.Reverse_LPWStr_With_LCID(local);
+                Assert.AreEqual(expected, actual);
+            }
+
+            CultureInfo culture = new CultureInfo("es-ES", false);
+            CultureInfo englishCulture = new CultureInfo("en-US", false);
+            CultureInfo oldCulture = CultureInfo.CurrentCulture;
+            try
+            {
+                CultureInfo.CurrentCulture = culture;
+                this.server.Pass_Through_LCID(out int lcid);
+                Assert.AreEqual(englishCulture.LCID, lcid); // CLR->COM LCID marshalling is explicitly hardcoded to en-US as requested by VSTO instead of passing the current culture.
+            }
+            finally
+            {
+                CultureInfo.CurrentCulture = oldCulture;
+            }
+        }
     }
 }
diff --git a/tests/src/Interop/COM/NETServer/DispatchTesting.cs b/tests/src/Interop/COM/NETServer/DispatchTesting.cs
new file mode 100644
index 0000000000..683fa88a9a
--- /dev/null
+++ b/tests/src/Interop/COM/NETServer/DispatchTesting.cs
@@ -0,0 +1,79 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Globalization;
+using System.Text;
+using System.Runtime.InteropServices;
+using Server.Contract;
+
+[ComVisible(true)]
+[Guid(Server.Contract.Guids.DispatchTesting)]
+public class DispatchTesting : Server.Contract.IDispatchTesting
+{
+    public void DoubleNumeric_ReturnByRef (
+        byte b1,
+        ref byte b2,
+        short s1,
+        ref short s2,
+        ushort us1,
+        ref ushort us2,
+        int i1,
+        ref int i2,
+        uint ui1,
+        ref uint ui2,
+        long l1,
+        ref long l2,
+        ulong ul1,
+        ref ulong ul2)
+    {
+        b2 = (byte)(b1 * 2);
+        s2 = (short)(s1 * 2);
+        us2 = (ushort)(us1 * 2);
+        i2 = i1 * 2;
+        ui2 = ui1 * 2;
+        l2 = l1 * 2;
+        ul2 = ul1 * 2;
+    }
+
+    public float Add_Float_ReturnAndUpdateByRef(float a, ref float b)
+    {
+        float sum = a + b;
+        b = sum;
+        return sum;
+    }
+    public double Add_Double_ReturnAndUpdateByRef(double a, ref double b)
+    {
+        double sum = a + b;
+        b = sum;
+        return sum;
+    }
+
+    public void TriggerException(IDispatchTesting_Exception excep, int errorCode)
+    {
+        switch (excep)
+        {
+        case IDispatchTesting_Exception.Disp:
+            throw new Exception();
+        case IDispatchTesting_Exception.HResult:
+            throw new System.ComponentModel.Win32Exception(errorCode);
+        }
+    }
+
+    // Special cases
+    public HFA_4 DoubleHVAValues(ref HFA_4 input)
+    {
+        input.x *= 2;
+        input.y *= 2;
+        input.z *= 2;
+        input.w *= 2;
+        return input;
+    }
+
+    [LCIDConversion(0)]
+    public int PassThroughLCID()
+    {
+        return CultureInfo.CurrentCulture.LCID;
+    }
+}
diff --git a/tests/src/Interop/COM/NETServer/StringTesting.cs b/tests/src/Interop/COM/NETServer/StringTesting.cs
index c47a155f29..e002ba0de9 100644
--- a/tests/src/Interop/COM/NETServer/StringTesting.cs
+++ b/tests/src/Interop/COM/NETServer/StringTesting.cs
@@ -3,6 +3,7 @@
 // See the LICENSE file in the project root for more information.
 
 using System;
+using System.Globalization;
 using System.Text;
 using System.Runtime.InteropServices;
 
@@ -191,4 +192,18 @@ public class StringTesting : Server.Contract.IStringTesting
     {
         b = Reverse(a);
     }
+
+    
+    [LCIDConversion(1)]
+    [return:MarshalAs(UnmanagedType.LPWStr)]
+    public string Reverse_LPWStr_With_LCID([MarshalAs(UnmanagedType.LPWStr)] string a)
+    {
+        return Reverse(a);
+    }
+
+    [LCIDConversion(0)]
+    public void Pass_Through_LCID(out int lcid)
+    {
+        lcid = CultureInfo.CurrentCulture.LCID;
+    }
 }
diff --git a/tests/src/Interop/COM/NativeClients/Dispatch.csproj b/tests/src/Interop/COM/NativeClients/Dispatch.csproj
new file mode 100644
index 0000000000..8fc786ad61
--- /dev/null
+++ b/tests/src/Interop/COM/NativeClients/Dispatch.csproj
@@ -0,0 +1,24 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Project ToolsVersion="12.0" DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+  <Import Project="$([MSBuild]::GetDirectoryNameOfFileAbove($(MSBuildThisFileDirectory), dir.props))\dir.props" />
+  <PropertyGroup>
+    <IgnoreCoreCLRTestLibraryDependency>true</IgnoreCoreCLRTestLibraryDependency>
+    <CLRTestScriptLocalCoreShim>true</CLRTestScriptLocalCoreShim>
+    <RequiresMockHostPolicy>true</RequiresMockHostPolicy>
+    <IlrtTestKind>BuildOnly</IlrtTestKind>
+
+    <TestUnsupportedOutsideWindows>true</TestUnsupportedOutsideWindows>
+    <DisableProjectBuild Condition="'$(TargetsUnix)' == 'true'">true</DisableProjectBuild>
+    <DefineConstants>BLOCK_WINDOWS_NANO</DefineConstants>
+  </PropertyGroup>
+  <ItemGroup>
+    <Compile Include="$(InteropCommonDir)ExeLauncherProgram.cs" />
+  </ItemGroup>
+  <ItemGroup>
+    <ProjectReference Include="Dispatch/CMakeLists.txt" />
+    <ProjectReference Include="../NetServer/NetServer.csproj" />
+    <ProjectReference Include="../../../Common/CoreCLRTestLibrary/CoreCLRTestLibrary.csproj" />
+  </ItemGroup>
+  <Import Project="$([MSBuild]::GetDirectoryNameOfFileAbove($(MSBuildThisFileDirectory), Interop.settings.targets))\Interop.settings.targets" />
+  <Import Project="$([MSBuild]::GetDirectoryNameOfFileAbove($(MSBuildThisFileDirectory), dir.targets))\dir.targets" />
+</Project>
diff --git a/tests/src/Interop/COM/NativeClients/Dispatch/App.manifest b/tests/src/Interop/COM/NativeClients/Dispatch/App.manifest
new file mode 100644
index 0000000000..ed665080a7
--- /dev/null
+++ b/tests/src/Interop/COM/NativeClients/Dispatch/App.manifest
@@ -0,0 +1,17 @@
+<?xml version="1.0" encoding="utf-8" standalone="yes" ?>
+<assembly xmlns="urn:schemas-microsoft-com:asm.v1" manifestVersion="1.0">
+  <assemblyIdentity
+    type="win32"
+    name="COMClientPrimitives"
+    version="1.0.0.0"/>
+
+  <dependency>
+    <dependentAssembly>
+      <!-- RegFree COM - CoreCLR Shim -->
+      <assemblyIdentity
+        type="win32"
+        name="CoreShim.X"
+        version="1.0.0.0"/>
+    </dependentAssembly>
+  </dependency>
+</assembly>
\ No newline at end of file
diff --git a/tests/src/Interop/COM/NativeClients/Dispatch/CMakeLists.txt b/tests/src/Interop/COM/NativeClients/Dispatch/CMakeLists.txt
new file mode 100644
index 0000000000..e6d874591f
--- /dev/null
+++ b/tests/src/Interop/COM/NativeClients/Dispatch/CMakeLists.txt
@@ -0,0 +1,18 @@
+cmake_minimum_required (VERSION 2.6)
+
+include_directories( ${INC_PLATFORM_DIR} )
+include_directories( "../../ServerContracts" )
+include_directories( "../../NativeServer" )
+set(SOURCES
+    Client.cpp
+    App.manifest)
+
+# add the executable
+add_executable (COMClientDispatch ${SOURCES})
+target_link_libraries(COMClientDispatch ${LINK_LIBRARIES_ADDITIONAL})
+
+# Copy CoreShim manifest to project output
+file(GENERATE OUTPUT ${CMAKE_CURRENT_BINARY_DIR}/$<CONFIG>/CoreShim.X.manifest INPUT ${CMAKE_CURRENT_SOURCE_DIR}/CoreShim.X.manifest)
+
+# add the install targets
+install (TARGETS COMClientDispatch DESTINATION bin)
diff --git a/tests/src/Interop/COM/NativeClients/Dispatch/Client.cpp b/tests/src/Interop/COM/NativeClients/Dispatch/Client.cpp
new file mode 100644
index 0000000000..de303fc37a
--- /dev/null
+++ b/tests/src/Interop/COM/NativeClients/Dispatch/Client.cpp
@@ -0,0 +1,309 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+#include "ClientTests.h"
+#include <memory>
+
+
+void Validate_Numeric_In_ReturnByRef();
+void Validate_Float_In_ReturnAndUpdateByRef();
+void Validate_Double_In_ReturnAndUpdateByRef();
+void Validate_LCID_Marshaled();
+
+template<COINIT TM>
+struct ComInit
+{
+    const HRESULT Result;
+
+    ComInit()
+        : Result{ ::CoInitializeEx(nullptr, TM) }
+    { }
+
+    ~ComInit()
+    {
+        if (SUCCEEDED(Result))
+            ::CoUninitialize();
+    }
+};
+
+using ComMTA = ComInit<COINIT_MULTITHREADED>;
+
+int __cdecl main()
+{
+    ComMTA init;
+    if (FAILED(init.Result))
+        return -1;
+
+    try
+    {
+        Validate_Numeric_In_ReturnByRef();
+        Validate_Float_In_ReturnAndUpdateByRef();
+        Validate_Double_In_ReturnAndUpdateByRef();
+        Validate_LCID_Marshaled();
+    }
+    catch (HRESULT hr)
+    {
+        ::printf("Test Failure: 0x%08x\n", hr);
+        return 101;
+    }
+
+    return 100;
+}
+
+void Validate_Numeric_In_ReturnByRef()
+{
+    HRESULT hr;
+
+    CoreShimComActivation csact{ W("NETServer"), W("DispatchTesting") };
+
+    ComSmartPtr<IDispatchTesting> dispatchTesting;
+    THROW_IF_FAILED(::CoCreateInstance(CLSID_DispatchTesting, nullptr, CLSCTX_INPROC, IID_IDispatchTesting, (void**)&dispatchTesting));
+
+    LPOLESTR numericMethodName = (LPOLESTR)W("DoubleNumeric_ReturnByRef");
+    LCID lcid = MAKELCID(LANG_USER_DEFAULT, SORT_DEFAULT);
+    DISPID methodId;
+
+    THROW_IF_FAILED(dispatchTesting->GetIDsOfNames(
+        IID_NULL,
+        &numericMethodName,
+        1,
+        lcid,
+        &methodId));
+    
+    BYTE b1 = 24;
+    BYTE b2;
+    SHORT s1 = 53;
+    SHORT s2;
+    USHORT us1 = 74;
+    USHORT us2;
+    LONG i1 = 34;
+    LONG i2;
+    ULONG ui1 = 854;
+    ULONG ui2;
+    LONGLONG l1 = 894;
+    LONGLONG l2;
+    ULONGLONG ul1 = 4168;
+    ULONGLONG ul2;
+
+    DISPPARAMS params;
+    params.cArgs = 14;
+    params.rgvarg = new VARIANTARG[params.cArgs];
+    params.cNamedArgs = 0;
+    params.rgdispidNamedArgs = nullptr;
+    
+    V_VT(&params.rgvarg[13]) = VT_UI1;
+    V_UI1(&params.rgvarg[13]) = b1;
+    V_VT(&params.rgvarg[12]) = VT_BYREF | VT_UI1;
+    V_UI1REF(&params.rgvarg[12]) = &b2;
+    V_VT(&params.rgvarg[11]) = VT_I2;
+    V_I2(&params.rgvarg[11]) = s1;
+    V_VT(&params.rgvarg[10]) = VT_BYREF | VT_I2;
+    V_I2REF(&params.rgvarg[10]) = &s2;
+    V_VT(&params.rgvarg[9]) = VT_UI2;
+    V_UI2(&params.rgvarg[9]) = us1;
+    V_VT(&params.rgvarg[8]) = VT_BYREF | VT_UI2;
+    V_UI2REF(&params.rgvarg[8]) = &us2;
+    V_VT(&params.rgvarg[7]) = VT_I4;
+    V_I4(&params.rgvarg[7]) = i1;
+    V_VT(&params.rgvarg[6]) = VT_BYREF | VT_I4;
+    V_I4REF(&params.rgvarg[6]) = &i2;
+    V_VT(&params.rgvarg[5]) = VT_UI4;
+    V_UI4(&params.rgvarg[5]) = ui1;
+    V_VT(&params.rgvarg[4]) = VT_BYREF | VT_UI4;
+    V_UI4REF(&params.rgvarg[4]) = &ui2;
+    V_VT(&params.rgvarg[3]) = VT_I8;
+    V_I8(&params.rgvarg[3]) = l1;
+    V_VT(&params.rgvarg[2]) = VT_BYREF | VT_I8;
+    V_I8REF(&params.rgvarg[2]) = &l2;
+    V_VT(&params.rgvarg[1]) = VT_UI8;
+    V_UI8(&params.rgvarg[1]) = ul1;
+    V_VT(&params.rgvarg[0]) = VT_BYREF | VT_UI8;
+    V_UI8REF(&params.rgvarg[0]) = &ul2;
+
+    THROW_IF_FAILED(dispatchTesting->Invoke(
+        methodId,
+        IID_NULL,
+        lcid,
+        DISPATCH_METHOD,
+        &params,
+        nullptr,
+        nullptr,
+        nullptr
+    ));
+
+    THROW_FAIL_IF_FALSE(b2 == b1 * 2);
+    THROW_FAIL_IF_FALSE(s2 == s1 * 2);
+    THROW_FAIL_IF_FALSE(us2 == us1 * 2);
+    THROW_FAIL_IF_FALSE(i2 == i1 * 2);
+    THROW_FAIL_IF_FALSE(ui2 == ui1 * 2);
+    THROW_FAIL_IF_FALSE(l2 == l1 * 2);
+    THROW_FAIL_IF_FALSE(ul2 == ul1 * 2);
+}
+
+namespace
+{
+    bool EqualByBound(float expected, float actual)
+    {
+        float low = expected - 0.0001f;
+        float high = expected + 0.0001f;
+        float eps = abs(expected - actual);
+        return eps < std::numeric_limits<float>::epsilon() || (low < actual && actual < high);
+    }
+
+    bool EqualByBound(double expected, double actual)
+    {
+        double low = expected - 0.00001;
+        double high = expected + 0.00001;
+        double eps = abs(expected - actual);
+        return eps < std::numeric_limits<double>::epsilon() || (low < actual && actual < high);
+    }
+}
+
+void Validate_Float_In_ReturnAndUpdateByRef()
+{
+    HRESULT hr;
+
+    CoreShimComActivation csact{ W("NETServer"), W("DispatchTesting") };
+
+    ComSmartPtr<IDispatchTesting> dispatchTesting;
+    THROW_IF_FAILED(::CoCreateInstance(CLSID_DispatchTesting, nullptr, CLSCTX_INPROC, IID_IDispatchTesting, (void**)&dispatchTesting));
+
+    LPOLESTR numericMethodName = (LPOLESTR)W("Add_Float_ReturnAndUpdateByRef");
+    LCID lcid = MAKELCID(LANG_USER_DEFAULT, SORT_DEFAULT);
+    DISPID methodId;
+
+    THROW_IF_FAILED(dispatchTesting->GetIDsOfNames(
+        IID_NULL,
+        &numericMethodName,
+        1,
+        lcid,
+        &methodId));
+    
+    float a = 12.34f;
+    float b = 1.234f;
+    float expected = b + a;
+
+    DISPPARAMS params;
+    params.cArgs = 2;
+    params.rgvarg = new VARIANTARG[params.cArgs];
+    params.cNamedArgs = 0;
+    params.rgdispidNamedArgs = nullptr;
+
+    VARIANT result;
+
+    V_VT(&params.rgvarg[1]) = VT_R4;
+    V_R4(&params.rgvarg[1]) = a;
+    V_VT(&params.rgvarg[0]) = VT_BYREF | VT_R4;
+    V_R4REF(&params.rgvarg[0]) = &b;
+
+
+    THROW_IF_FAILED(dispatchTesting->Invoke(
+        methodId,
+        IID_NULL,
+        lcid,
+        DISPATCH_METHOD,
+        &params,
+        &result,
+        nullptr,
+        nullptr
+    ));
+
+    THROW_FAIL_IF_FALSE(EqualByBound(expected, V_R4(&result)));
+    THROW_FAIL_IF_FALSE(EqualByBound(expected, b));
+}
+
+void Validate_Double_In_ReturnAndUpdateByRef()
+{
+    HRESULT hr;
+
+    CoreShimComActivation csact{ W("NETServer"), W("DispatchTesting") };
+
+    ComSmartPtr<IDispatchTesting> dispatchTesting;
+    THROW_IF_FAILED(::CoCreateInstance(CLSID_DispatchTesting, nullptr, CLSCTX_INPROC, IID_IDispatchTesting, (void**)&dispatchTesting));
+
+    LPOLESTR numericMethodName = (LPOLESTR)W("Add_Double_ReturnAndUpdateByRef");
+    LCID lcid = MAKELCID(LANG_USER_DEFAULT, SORT_DEFAULT);
+    DISPID methodId;
+
+    THROW_IF_FAILED(dispatchTesting->GetIDsOfNames(
+        IID_NULL,
+        &numericMethodName,
+        1,
+        lcid,
+        &methodId));
+    
+    double a = 1856.5634;
+    double b = 587867.757;
+    double expected = a + b;
+
+    DISPPARAMS params;
+    params.cArgs = 2;
+    params.rgvarg = new VARIANTARG[params.cArgs];
+    params.cNamedArgs = 0;
+    params.rgdispidNamedArgs = nullptr;
+
+    VARIANT result;
+
+    V_VT(&params.rgvarg[1]) = VT_R8;
+    V_R8(&params.rgvarg[1]) = a;
+    V_VT(&params.rgvarg[0]) = VT_BYREF | VT_R8;
+    V_R8REF(&params.rgvarg[0]) = &b;
+
+
+    THROW_IF_FAILED(dispatchTesting->Invoke(
+        methodId,
+        IID_NULL,
+        lcid,
+        DISPATCH_METHOD,
+        &params,
+        &result,
+        nullptr,
+        nullptr
+    ));
+
+    THROW_FAIL_IF_FALSE(EqualByBound(expected, V_R8(&result)));
+    THROW_FAIL_IF_FALSE(EqualByBound(expected, b));
+}
+
+void Validate_LCID_Marshaled()
+{
+    HRESULT hr;
+
+    CoreShimComActivation csact{ W("NETServer"), W("DispatchTesting") };
+
+    ComSmartPtr<IDispatchTesting> dispatchTesting;
+    THROW_IF_FAILED(::CoCreateInstance(CLSID_DispatchTesting, nullptr, CLSCTX_INPROC, IID_IDispatchTesting, (void**)&dispatchTesting));
+
+    LPOLESTR numericMethodName = (LPOLESTR)W("PassThroughLCID");
+    LCID lcid = MAKELCID(MAKELANGID(LANG_SPANISH, SUBLANG_SPANISH_CHILE), SORT_DEFAULT);
+    DISPID methodId;
+
+    THROW_IF_FAILED(dispatchTesting->GetIDsOfNames(
+        IID_NULL,
+        &numericMethodName,
+        1,
+        lcid,
+        &methodId));
+
+    DISPPARAMS params;
+    params.cArgs = 0;
+    params.rgvarg = nullptr;
+    params.cNamedArgs = 0;
+    params.rgdispidNamedArgs = nullptr;
+
+    VARIANT result;
+
+    THROW_IF_FAILED(dispatchTesting->Invoke(
+        methodId,
+        IID_NULL,
+        lcid,
+        DISPATCH_METHOD,
+        &params,
+        &result,
+        nullptr,
+        nullptr
+    ));
+
+    THROW_FAIL_IF_FALSE(lcid == V_I4(&result));
+}
diff --git a/tests/src/Interop/COM/NativeClients/Dispatch/ClientTests.h b/tests/src/Interop/COM/NativeClients/Dispatch/ClientTests.h
new file mode 100644
index 0000000000..58a524ec0b
--- /dev/null
+++ b/tests/src/Interop/COM/NativeClients/Dispatch/ClientTests.h
@@ -0,0 +1,13 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+#include <xplatform.h>
+#include <cassert>
+#include <Server.Contracts.h>
+
+#define COM_CLIENT
+#include <Servers.h>
+
+#define THROW_IF_FAILED(exp) { hr = exp; if (FAILED(hr)) { ::printf("FAILURE: 0x%08x = %s\n", hr, #exp); throw hr; } }
+#define THROW_FAIL_IF_FALSE(exp) { if (!(exp)) { ::printf("FALSE: %s\n", #exp); throw E_FAIL; } }
diff --git a/tests/src/Interop/COM/NativeClients/Dispatch/CoreShim.X.manifest b/tests/src/Interop/COM/NativeClients/Dispatch/CoreShim.X.manifest
new file mode 100644
index 0000000000..0e635e03c3
--- /dev/null
+++ b/tests/src/Interop/COM/NativeClients/Dispatch/CoreShim.X.manifest
@@ -0,0 +1,16 @@
+<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<assembly xmlns="urn:schemas-microsoft-com:asm.v1" manifestVersion="1.0">
+
+<assemblyIdentity
+  type="win32"
+  name="CoreShim.X"
+  version="1.0.0.0" />
+
+<file name="CoreShim.dll">
+  <!-- DispatchTesting -->
+  <comClass
+    clsid="{0F8ACD0C-ECE0-4F2A-BD1B-6BFCA93A0726}"
+    threadingModel="Both" />
+</file>
+
+</assembly>
diff --git a/tests/src/Interop/COM/NativeClients/Primitives/StringTests.cpp b/tests/src/Interop/COM/NativeClients/Primitives/StringTests.cpp
index b003130d48..3bef3d7e0b 100644
--- a/tests/src/Interop/COM/NativeClients/Primitives/StringTests.cpp
+++ b/tests/src/Interop/COM/NativeClients/Primitives/StringTests.cpp
@@ -406,6 +406,32 @@ namespace
             THROW_FAIL_IF_FALSE(local == actual);
         }
     }
+
+    void Marshal_LCID(_In_ IStringTesting* stringTesting)
+    {
+        ::printf("Marshal LCIDs\n");
+
+        HRESULT hr;
+
+        LCID lcid = MAKELCID(MAKELANGID(LANG_SPANISH, SUBLANG_SPANISH_CHILE), SORT_DEFAULT);
+
+        WStr r = GetReversableStrings<WStr>()[0];
+        WStr local{ r };
+
+        WStr actual;
+        WStr expected;
+        THROW_IF_FAILED(r.Reverse(expected));
+
+        LPWSTR tmp;
+        THROW_IF_FAILED(stringTesting->Reverse_LPWSTR_With_LCID(local, lcid, &tmp));
+        actual.Attach(tmp);
+        THROW_FAIL_IF_FALSE(expected == actual);
+
+        LCID actualLcid;
+
+        THROW_IF_FAILED(stringTesting->Pass_Through_LCID(lcid, &actualLcid));
+        THROW_FAIL_IF_FALSE(lcid == actualLcid);
+    }
 }
 
 void Run_StringTests()
@@ -420,4 +446,5 @@ void Run_StringTests()
     Marshal_LPString(stringTesting);
     Marshal_LPWString(stringTesting);
     Marshal_BStrString(stringTesting);
+    Marshal_LCID(stringTesting);
 }
diff --git a/tests/src/Interop/COM/NativeServer/DispatchTesting.h b/tests/src/Interop/COM/NativeServer/DispatchTesting.h
index 166d6fa749..cf6cefe2d8 100644
--- a/tests/src/Interop/COM/NativeServer/DispatchTesting.h
+++ b/tests/src/Interop/COM/NativeServer/DispatchTesting.h
@@ -108,6 +108,10 @@ public: // IDispatch
             {
                 return DoubleHVAValues_Proxy(pDispParams, pVarResult);
             }
+            case 6:
+            {
+                return PassThroughLCID_Proxy(lcid, pVarResult);
+            }
             }
 
             return E_NOTIMPL;
@@ -410,6 +414,13 @@ private:
         return DoubleHVAValues(args[0], (HFA_4*)&pVarResult->pvRecord);
     }
 
+    HRESULT PassThroughLCID_Proxy(_In_ LCID lcid, _Inout_ VARIANT* pVarResult)
+    {
+        V_VT(pVarResult) = VT_I4;
+        V_I4(pVarResult) = lcid;
+        return S_OK;
+    }
+
 public: // IUnknown
     STDMETHOD(QueryInterface)(
         /* [in] */ REFIID riid,
@@ -428,7 +439,8 @@ const WCHAR * const DispatchTesting::Names[] =
     W("Add_Float_ReturnAndUpdateByRef"),
     W("Add_Double_ReturnAndUpdateByRef"),
     W("TriggerException"),
-    W("DoubleHVAValues")
+    W("DoubleHVAValues"),
+    W("PassThroughLCID")
 };
 
 const int DispatchTesting::NamesCount = ARRAYSIZE(DispatchTesting::Names);
diff --git a/tests/src/Interop/COM/NativeServer/StringTesting.h b/tests/src/Interop/COM/NativeServer/StringTesting.h
index cd01fbe317..1c1f9c1cff 100644
--- a/tests/src/Interop/COM/NativeServer/StringTesting.h
+++ b/tests/src/Interop/COM/NativeServer/StringTesting.h
@@ -312,6 +312,22 @@ public: // IStringTesting
         return S_OK;
     }
 
+    DEF_FUNC(Reverse_LPWSTR_With_LCID)(
+        /*[in]*/ LPWSTR a,
+        /*[in]*/ LCID lcid, // This parameter is only used as a placeholder to check that we've injected it into the correct arg slot.
+        /*[out]*/ LPWSTR*  b)
+    {
+        return Reverse_LPWStr(a, b);
+    }
+
+    DEF_FUNC(Pass_Through_LCID)(
+        /*[in]*/ LCID lcidFromCulture,
+        /*[out]*/ LCID* outLcid)
+    {
+        *outLcid = lcidFromCulture;
+        return S_OK;
+    }
+
 public: // IUnknown
     STDMETHOD(QueryInterface)(
         /* [in] */ REFIID riid,
diff --git a/tests/src/Interop/COM/ServerContracts/Server.Contracts.cs b/tests/src/Interop/COM/ServerContracts/Server.Contracts.cs
index f16007f38e..89a28a7c68 100644
--- a/tests/src/Interop/COM/ServerContracts/Server.Contracts.cs
+++ b/tests/src/Interop/COM/ServerContracts/Server.Contracts.cs
@@ -176,6 +176,13 @@ namespace Server.Contract
         void Reverse_BStr_Out([MarshalAs(UnmanagedType.BStr)] string a, [MarshalAs(UnmanagedType.BStr)] out string b);
 
         void Reverse_BStr_OutAttr([MarshalAs(UnmanagedType.BStr)] string a, [Out][MarshalAs(UnmanagedType.BStr)] string b);
+
+        [LCIDConversion(1)]
+        [return: MarshalAs(UnmanagedType.LPWStr)]
+        string Reverse_LPWStr_With_LCID([MarshalAs(UnmanagedType.LPWStr)] string a);
+
+        [LCIDConversion(0)]
+        void Pass_Through_LCID(out int lcid);
     }
 
     public struct HResult
@@ -239,6 +246,9 @@ namespace Server.Contract
 
         // Special cases
         HFA_4 DoubleHVAValues(ref HFA_4 input);
+
+        [LCIDConversion(0)]
+        int PassThroughLCID();
     }
 
     [ComVisible(true)]
diff --git a/tests/src/Interop/COM/ServerContracts/Server.Contracts.h b/tests/src/Interop/COM/ServerContracts/Server.Contracts.h
index b2c258d7be..90df20e18e 100644
--- a/tests/src/Interop/COM/ServerContracts/Server.Contracts.h
+++ b/tests/src/Interop/COM/ServerContracts/Server.Contracts.h
@@ -356,6 +356,13 @@ IStringTesting : IUnknown
       virtual HRESULT STDMETHODCALLTYPE Reverse_BStr_OutAttr (
         /*[in]*/ BSTR a,
         /*[out]*/ BSTR b ) = 0;
+      virtual HRESULT STDMETHODCALLTYPE Reverse_LPWSTR_With_LCID (
+          /*[in]*/ LPWSTR a,
+          /*[in]*/ LCID lcid,
+          /*[out]*/ LPWSTR*  b) = 0;
+      virtual HRESULT STDMETHODCALLTYPE Pass_Through_LCID(
+        /*[in]*/ LCID lcidFromCulture,
+        /*[out]*/ LCID* outLcid) = 0;
 };
 
 struct __declspec(uuid("592386a5-6837-444d-9de3-250815d18556"))
diff --git a/tests/src/Interop/PInvoke/Attributes/LCID/LCIDNative.cpp b/tests/src/Interop/PInvoke/Attributes/LCID/LCIDNative.cpp
index 77f873553e..028bb466cb 100644
--- a/tests/src/Interop/PInvoke/Attributes/LCID/LCIDNative.cpp
+++ b/tests/src/Interop/PInvoke/Attributes/LCID/LCIDNative.cpp
@@ -2,119 +2,36 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-#include <stdio.h>
-#include <tchar.h>
-#include <windows.h>
 #include <xplatform.h>
+#include <algorithm>
 
-const char* strManaged = "Managed\0String\0";
-size_t lenstrManaged = 7; // the length of strManaged
-
-const char* strReturn = "a\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0";
-const char* strFalseReturn = "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0";
-
-const char* strNative = " Native\0String\0";
-size_t lenstrNative = 7; //the len of strNative
-
-extern "C" LPSTR ReturnString()
-{
-    size_t lenstrReturn = strlen(strReturn);
-    LPSTR ret = (LPSTR)(CoTaskMemAlloc(sizeof(char)*(lenstrReturn+1)));
-    memset(ret,'\0',lenstrReturn+1);
-    strncpy_s(ret,lenstrReturn + 1,strReturn,1);
-    return ret;
-}
-
-extern "C" LPSTR ReturnFalseString()
-{
-    size_t lenstrFalseReturn = strlen(strFalseReturn);
-    LPSTR ret = (LPSTR)(CoTaskMemAlloc(sizeof(char)*(lenstrFalseReturn+1)));
-    memset(ret,'\0',lenstrFalseReturn+1);
-    strncpy_s(ret,lenstrFalseReturn + 1,strFalseReturn,1);
-    return ret;
-}
-
-extern "C" void PrintExpectedAndActual(LPCSTR s, size_t len)
+void Reverse(LPCWSTR str, LPWSTR *res)
 {
-    //Expected
-    printf("Expected:");
-    for(size_t i = 0; i< lenstrManaged;++i)
-        putchar(*(((const char *)strManaged)+i));
-    printf("\tThe length of Expected:%d\n",static_cast<int>(lenstrManaged));
-
-    //Actual
-    printf("Actual:");
-    for(size_t j = 0; j < len; ++j )
-        putchar(*(((const char *)s) + j));
-    printf("\tThe length of Actual:%d\n",static_cast<int>(len));
-}
-
-extern "C" DLL_EXPORT LPSTR STDMETHODCALLTYPE MarshalStringBuilder_LCID_As_First_Argument(int lcid, LPSTR s)
-{
-    printf("LCID:%d\n\n",lcid);
-
-    //Check the Input
-    size_t len = strlen(s);
-    if((len != lenstrManaged)||(memcmp(s,strManaged,len)!=0))
+    LPCWSTR tmp = str;
+    size_t len = 0;
+    while (*tmp++)
+        ++len;
+
+    size_t strDataLen = (len + 1) * sizeof(str[0]);
+    auto resLocal = (LPWSTR)CoreClrAlloc(strDataLen);
+    if (resLocal == nullptr)
     {
-        printf("Error in Function MarshalStringBuilder_LCID_As_First_Argument(Native Client)\n");
-        PrintExpectedAndActual(s, len);
-        return ReturnFalseString();
+        *res = nullptr;
+        return;
     }
 
-    //In-Place Change
-    strncpy_s(s,len + 1,strNative,lenstrNative);
-
-    //Return
-    return ReturnString();
+    memcpy(resLocal, str, strDataLen);
+    
+    std::reverse(resLocal, resLocal + len);
+    *res = resLocal;
 }
 
-extern "C" DLL_EXPORT LPSTR STDMETHODCALLTYPE MarshalStringBuilder_LCID_As_Last_Argument_SetLastError(LPSTR s,int lcid)
-{	
-    //Check the Input
-    size_t len = strlen(s);
-    if((len != lenstrManaged)||(memcmp(s,strManaged,len)!=0))
-    {
-        printf("Error in Function MarshalStringBuilder_LCID_As_Last_Argument_SetLastError(Native Client)\n");
-        PrintExpectedAndActual(s, len);
-        return ReturnFalseString();
-    }
-
-    //In-Place Change
-    strncpy_s(s,len + 1,strNative,lenstrNative);
-
-    SetLastError(1090);
-    //Return
-    return ReturnString();
+extern "C" void DLL_EXPORT ReverseString(LPCWSTR str, LCID lcid, LPWSTR* reversed)
+{
+    Reverse(str, reversed);
 }
 
-extern "C" DLL_EXPORT HRESULT STDMETHODCALLTYPE MarshalStringBuilder_LCID_PreserveSig_SetLastError(LPSTR s, int lcid, LPSTR * retVal)
+extern "C" BOOL DLL_EXPORT VerifyValidLCIDPassed(LCID actual, LCID expected)
 {
-    //Check the Input
-    size_t len = strlen(s);
-    if((len != lenstrManaged)||(memcmp(s,strManaged,len)!=0))
-    {
-        printf("Error in Function MarshalStringBuilder_LCID_PreserveSig_SetLastError\n");
-        PrintExpectedAndActual(s, len);
-
-        size_t lenstrFalseReturn = strlen(ReturnFalseString());
-        *retVal = (LPSTR)CoTaskMemAlloc(sizeof(char)*(lenstrFalseReturn+1));
-        memset(*retVal,'\0',lenstrFalseReturn+1);
-        strncpy_s(*retVal,lenstrFalseReturn,ReturnFalseString(),lenstrFalseReturn);
-
-        return S_FALSE;
-    }
-
-    //In-Place Change
-    strncpy_s(s,len + 1,strNative,lenstrNative);
-
-    //Set the error code.
-    SetLastError(1090);
-
-    size_t lenstrReturn = strlen(ReturnString());
-    *retVal = (LPSTR)(CoTaskMemAlloc(sizeof(char)*(lenstrReturn+1)));
-    memset(*retVal,'\0',lenstrReturn+1);
-    strncpy_s(*retVal,lenstrReturn + 1,ReturnString(),lenstrReturn);
-
-    return S_OK;
+    return actual == expected;
 }
diff --git a/tests/src/Interop/PInvoke/Attributes/LCID/LCIDTest.cs b/tests/src/Interop/PInvoke/Attributes/LCID/LCIDTest.cs
index 15c75e9a31..fdf35bbbe0 100644
--- a/tests/src/Interop/PInvoke/Attributes/LCID/LCIDTest.cs
+++ b/tests/src/Interop/PInvoke/Attributes/LCID/LCIDTest.cs
@@ -2,183 +2,57 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-//The testcase focus test the BStr with embed null string
-using System.Runtime.InteropServices;
 using System;
+using System.Globalization;
 using System.Reflection;
+using System.Runtime.InteropServices;
 using System.Text;
+using TestLibrary;
 
-class LCIDTest
+class LCIDNative
 {
-    [DllImport(@"LCIDNative.dll", EntryPoint = "MarshalStringBuilder_LCID_As_First_Argument")]
-    [LCIDConversionAttribute(0)]
-    [return: MarshalAs(UnmanagedType.LPStr)]
-    private static extern StringBuilder MarshalStringBuilder_LCID_As_First_Argument([In, Out][MarshalAs(UnmanagedType.LPStr)]StringBuilder s);
-
-    [DllImport(@"LCIDNative.dll", EntryPoint = "MarshalStringBuilder_LCID_As_Last_Argument_SetLastError")]
-    [LCIDConversionAttribute(1)]
-    [return: MarshalAs(UnmanagedType.LPStr)]
-    private static extern StringBuilder MarshalStringBuilder_LCID_As_Last_Argument([In, Out][MarshalAs(UnmanagedType.LPStr)]StringBuilder s);
-
-    [DllImport(@"LCIDNative.dll", EntryPoint = "MarshalStringBuilder_LCID_As_Last_Argument_SetLastError", SetLastError = true)]
-    [LCIDConversionAttribute(1)]
-    [return: MarshalAs(UnmanagedType.LPStr)]
-    private static extern StringBuilder MarshalStringBuilder_LCID_As_Last_Argument_SetLastError([In, Out][MarshalAs(UnmanagedType.LPStr)]StringBuilder s);
-
-    [DllImport(@"LCIDNative.dll", EntryPoint = "MarshalStringBuilder_LCID_PreserveSig_SetLastError", PreserveSig = false, SetLastError = true)]
-    [LCIDConversionAttribute(1)]
-    [return: MarshalAs(UnmanagedType.LPStr)]
-    private static extern StringBuilder MarshalStringBuilder_LCID_PreserveSig_SetLastError([In, Out][MarshalAs(UnmanagedType.LPStr)]StringBuilder s);
-
-    //LCID as first argument
-    static bool Scenario1()
-    {
-        Console.WriteLine("Scenairo1 started");
-
-        string strManaged = "Managed";
-        StringBuilder expectedStrRet = new StringBuilder("a", 1);
-        string strNative = " Native";
-        StringBuilder strBNative = new StringBuilder(" Native", 7);
-
-        StringBuilder strPara = new StringBuilder(strManaged, strManaged.Length);
-        StringBuilder strRet = MarshalStringBuilder_LCID_As_First_Argument(strPara);
-
-        if (expectedStrRet.ToString() != strRet.ToString())
-        {
-            Console.WriteLine("Method MarshalStringBuilder_LCID_As_First_Argument[Managed Side],The Return string is wrong");
-            return false;
-        }
-
-        if (strBNative.ToString() != strPara.ToString())
-        {
-            Console.WriteLine("Method MarshalStringBuilder_LCID_As_First_Argument[Managed Side],The Passed string is wrong");
-            return false;
-        }
+    [DllImport(nameof(LCIDNative), CharSet = CharSet.Unicode)]
+    [LCIDConversion(1)]
+    public static extern void ReverseString(string str, out string result);
 
-        Console.WriteLine("Scenairo1 success");
-        return true;
-    }
-
-    //LCID as last argument
-    static bool Scenario2()
-    {
-        Console.WriteLine("Scenairo2 started");
-
-        string strManaged = "Managed";
-        StringBuilder expectedStrRet = new StringBuilder("a", 1);
-        string strNative = " Native";
-        StringBuilder strBNative = new StringBuilder(" Native", 7);
-
-        StringBuilder strPara = new StringBuilder(strManaged, strManaged.Length);
-        StringBuilder strRet = MarshalStringBuilder_LCID_As_Last_Argument(strPara);
-
-        if (expectedStrRet.ToString() != strRet.ToString())
-        {
-            Console.WriteLine("Method MarshalStringBuilder_LCID_As_Last_Argument[Managed Side],The Return string is wrong");
-            return false;
-        }
-
-        if (strBNative.ToString() != strPara.ToString())
-        {
-            Console.WriteLine("Method MarshalStringBuilder_LCID_As_Last_Argument[Managed Side],The Passed string is wrong");
-            return false;
-        }
-
-        //Verify that error value is set.
-        int result = Marshal.GetLastWin32Error();
-        if (result != 0)
-        {
-            Console.WriteLine("MarshalStringBuilder_LCID_As_Last_Argument: GetLasterror returned wrong error code");
-            return false;
-        }
-
-        Console.WriteLine("Scenairo2 success");
-        return true;
-    }
-
-    //SetLastError =true
-    static bool Scenario3()
-    {
-        Console.WriteLine("Scenairo3 started");
-
-        string strManaged = "Managed";
-        StringBuilder expectedStrRet = new StringBuilder("a", 1);
-        string strNative = " Native";
-        StringBuilder strBNative = new StringBuilder(" Native", 7);
-
-        StringBuilder strPara = new StringBuilder(strManaged, strManaged.Length);
-        StringBuilder strRet = MarshalStringBuilder_LCID_As_Last_Argument_SetLastError(strPara);
-
-        if (expectedStrRet.ToString() != strRet.ToString())
-        {
-            Console.WriteLine("Method MarshalStringBuilder_LCID_As_Last_Argument_SetLastError[Managed Side],The Return string is wrong");
-            return false;
-        }
-
-        if (strBNative.ToString() != strPara.ToString())
-        {
-            Console.WriteLine("Method MarshalStringBuilder_LCID_As_Last_Argument_SetLastError[Managed Side],The Passed string is wrong");
-            return false;
-        }
-
-        //Verify that error value is set.
-        int result = Marshal.GetLastWin32Error();
-        if (result != 1090)
-        {
-            Console.WriteLine("MarshalStringBuilder_LCID_As_Last_Argument_SetLastError: GetLasterror returned wrong error code");
-            return false;
-        }
-
-        Console.WriteLine("Scenairo3 success");
-        return true;
-    }
+    [DllImport(nameof(LCIDNative), CharSet = CharSet.Unicode)]
+    [LCIDConversion(0)]
+    public static extern bool VerifyValidLCIDPassed(int lcid);
+}
 
-    //PreserveSig = false, SetLastError = true
-    static bool Scenario4()
+class LCIDTest
+{
+    private static string Reverse(string s)
     {
-        Console.WriteLine("Scenairo4 started");
-
-        string strManaged = "Managed";
-        StringBuilder expectedStrRet = new StringBuilder("a", 1);
-        string strNative = " Native";
-        StringBuilder strBNative = new StringBuilder(" Native", 7);
-
-        StringBuilder strPara = new StringBuilder(strManaged, strManaged.Length);
-        StringBuilder strRet = MarshalStringBuilder_LCID_PreserveSig_SetLastError(strPara);
-
-
-        if (expectedStrRet.ToString() != strRet.ToString())
-        {
-            Console.WriteLine("Method MarshalStringBuilder_LCID_As_Last_Argument_SetLastError[Managed Side],The Return string is wrong");
-            return false;
-        }
-
-        if (strBNative.ToString() != strPara.ToString())
-        {
-            Console.WriteLine("Method MarshalStringBuilder_LCID_As_Last_Argument_SetLastError[Managed Side],The Passed string is wrong");
-            return false;
-        }
-
-        //Verify that error value is set.
-        int result = Marshal.GetLastWin32Error();
-        if (result != 1090)
-        {
-            Console.WriteLine("MarshalStringBuilder_LCID_As_Last_Argument_SetLastError: GetLasterror returned wrong error code");
-            return false;
-        }
-        
-        Console.WriteLine("Scenairo4 success");
-        return true;
+        var chars = s.ToCharArray();
+        Array.Reverse(chars);
+        return new string(chars);
     }
 
-    public static int Main(string[] args)
+    public static int Main()
     {
-        var success = true;
-        success = success && Scenario1();
-        success = success && Scenario2();
-        success = success && Scenario3();
-        success = success && Scenario4();
-
-        return success ? 100 : 101;
+        try
+        {
+            string testString = "Test string";
+            LCIDNative.ReverseString(testString, out string reversed);
+            Assert.AreEqual(Reverse(testString), reversed);
+            CultureInfo originalCulture = CultureInfo.CurrentCulture;
+            try
+            {
+                CultureInfo spanishCulture = new CultureInfo("es-ES", false);
+                CultureInfo.CurrentCulture = spanishCulture;
+                Assert.IsTrue(LCIDNative.VerifyValidLCIDPassed(CultureInfo.CurrentCulture.LCID));
+            }
+            finally
+            {
+                CultureInfo.CurrentCulture = originalCulture;
+            }
+        }
+        catch (System.Exception e)
+        {
+            Console.WriteLine(e.ToString());
+            return 101;
+        }
+        return 100;
     }
 }
diff --git a/tests/src/Interop/PInvoke/Attributes/LCID/LCIDTest.csproj b/tests/src/Interop/PInvoke/Attributes/LCID/LCIDTest.csproj
index 5c446314db..642c209df3 100644
--- a/tests/src/Interop/PInvoke/Attributes/LCID/LCIDTest.csproj
+++ b/tests/src/Interop/PInvoke/Attributes/LCID/LCIDTest.csproj
@@ -1,6 +1,7 @@
 <?xml version="1.0" encoding="utf-8"?>
 <Project ToolsVersion="12.0" DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
   <Import Project="$([MSBuild]::GetDirectoryNameOfFileAbove($(MSBuildThisFileDirectory), dir.props))\dir.props" />
+  <Import Project="$([MSBuild]::GetDirectoryNameOfFileAbove($(MSBuildThisFileDirectory), Interop.settings.targets))\Interop.settings.targets" />
   <PropertyGroup>
     <Configuration Condition=" '$(Configuration)' == '' ">Debug</Configuration>
     <Platform Condition=" '$(Platform)' == '' ">AnyCPU</Platform>