Imported Upstream version 4.6.0.125

Former-commit-id: a2155e9bd80020e49e72e86c44da02a8ac0e57a4

mcs/class/referencesource/System.Xml/System/Xml/Ref.cs

@@ -0,0 +1,29 @@
+//------------------------------------------------------------------------------
+// <copyright file="Ref.cs" company="Microsoft">
+//     Copyright (c) Microsoft Corporation.  All rights reserved.
+// </copyright>
+// <owner current="true" primary="true">[....]</owner>
+//------------------------------------------------------------------------------
+
+using System.Diagnostics;
+
+namespace System.Xml {
+
+    /// <summary>
+    /// Ref class is used to verify string atomization in debug mode.
+    /// </summary>
+    internal static class Ref {
+        public static bool Equal(string strA, string strB) {
+        #if DEBUG
+            if (((object) strA != (object) strB) && string.Equals(strA, strB))
+                Debug.Assert(false, "Ref.Equal: Object comparison used for non-atomized string '" + strA + "'");
+        #endif
+            return (object) strA == (object) strB;
+        }
+
+        // Prevent typos. If someone uses Ref.Equals instead of Ref.Equal,
+        // the program would not compile.
+        public static new void Equals(object objA, object objB) {
+        }
+    }
+}