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diff --git a/src/mscorlib/src/System/Collections/Generic/IComparer.cs b/src/mscorlib/src/System/Collections/Generic/IComparer.cs
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+// 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.
+
+/*============================================================
+**
+** Interface:  IComparer
+** 
+** 
+**
+**
+** Purpose: Interface for comparing two generic Objects.
+**
+** 
+===========================================================*/
+namespace System.Collections.Generic {
+    
+    using System;
+    // The generic IComparer interface implements a method that compares 
+    // two objects. It is used in conjunction with the Sort and 
+    // BinarySearch methods on the Array, List, and SortedList classes.
+    public interface IComparer<in T>
+    {
+        // Compares two objects. An implementation of this method must return a
+        // value less than zero if x is less than y, zero if x is equal to y, or a
+        // value greater than zero if x is greater than y.
+        // 
+        int Compare(T x, T y);
+    }
+}