1 files changed, 68 insertions, 0 deletions
diff --git a/src/mscorlib/src/System/Runtime/InteropServices/WindowsRuntime/MapViewToReadOnlyCollectionAdapter.cs b/src/mscorlib/src/System/Runtime/InteropServices/WindowsRuntime/MapViewToReadOnlyCollectionAdapter.cs
new file mode 100644
index 0000000000..58427fbd71
--- /dev/null
+++ b/src/mscorlib/src/System/Runtime/InteropServices/WindowsRuntime/MapViewToReadOnlyCollectionAdapter.cs
@@ -0,0 +1,68 @@
+// 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.Security;
+using System.Collections;
+using System.Collections.Generic;
+using System.Diagnostics.Contracts;
+using System.Runtime.InteropServices;
+using System.Runtime.CompilerServices;
+
+namespace System.Runtime.InteropServices.WindowsRuntime
+{
+    // These stubs will be used when a call via IReadOnlyCollection<KeyValuePair<K, V>> is made in managed code.
+    // This can mean two things - either the underlying unmanaged object implements IMapView<K, V> or it
+    // implements IVectorView<IKeyValuePair<K, V>> and we cannot determine this statically in the general
+    // case so we have to cast at run-time. Used by the interop mashaling infrastructure.
+    //
+    // The methods on this class must be written VERY carefully to avoid introducing security holes.
+    // That's because they are invoked with special "this"! The "this" object
+    // for all of these methods are not MapViewToReadOnlyCollectionAdapter objects. Rather, they are of type
+    // IVectorView<KeyValuePair<K, V>> or IMapView<K, V>. No actual MapViewToReadOnlyCollectionAdapter object is ever
+    // instantiated. Thus, you will see a lot of expressions that cast "this" to "IVectorView<KeyValuePair<K, V>>"
+    // or "IMapView<K, V>".
+    internal sealed class MapViewToReadOnlyCollectionAdapter
+    {
+        private MapViewToReadOnlyCollectionAdapter()
+        {
+            Contract.Assert(false, "This class is never instantiated");
+        }
+
+        // int Count { get }
+        [Pure]
+        [SecurityCritical]
+        internal int Count<K, V>()
+        {
+            object _this = JitHelpers.UnsafeCast<object>(this);
+
+            IMapView<K, V> _this_map = _this as IMapView<K, V>;
+            if (_this_map != null)
+            {
+                uint size = _this_map.Size;
+
+                if (((uint)Int32.MaxValue) < size)
+                {
+                    throw new InvalidOperationException(Environment.GetResourceString("InvalidOperation_CollectionBackingDictionaryTooLarge"));
+                }
+
+                return (int)size;
+            }
+            else
+            {
+                IVectorView<KeyValuePair<K, V>> _this_vector = JitHelpers.UnsafeCast<IVectorView<KeyValuePair<K, V>>>(this);
+                uint size = _this_vector.Size;
+
+                if (((uint)Int32.MaxValue) < size)
+                {
+                    throw new InvalidOperationException(Environment.GetResourceString("InvalidOperation_CollectionBackingListTooLarge"));
+                }
+
+                return (int)size;
+            }
+        }
+    }
+}