1 files changed, 16 insertions, 0 deletions
diff --git a/src/mscorlib/shared/System/Collections/IEqualityComparer.cs b/src/mscorlib/shared/System/Collections/IEqualityComparer.cs
new file mode 100644
index 0000000000..35513f577d
--- /dev/null
+++ b/src/mscorlib/shared/System/Collections/IEqualityComparer.cs
@@ -0,0 +1,16 @@
+// 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;
+
+namespace System.Collections
+{
+    // An IEqualityComparer is a mechanism to consume custom performant comparison infrastructure
+    // that can be consumed by some of the common collections.
+    public interface IEqualityComparer
+    {
+        bool Equals(Object x, Object y);
+        int GetHashCode(Object obj);
+    }
+}