Imported Upstream version 4.6.0.125

Former-commit-id: a2155e9bd80020e49e72e86c44da02a8ac0e57a4

mcs/class/referencesource/System.Web/Util/EmptyCollection.cs

@@ -0,0 +1,42 @@
+//------------------------------------------------------------------------------
+// <copyright file="EmptyCollection.cs" company="Microsoft">
+//     Copyright (c) Microsoft Corporation.  All rights reserved.
+// </copyright>                                                                
+//------------------------------------------------------------------------------
+
+/*
+ * EmptyCollection class
+ * 
+ * Copyright (c) 1999 Microsoft Corporation
+ */
+
+namespace System.Web.Util {
+
+using System.Collections;
+
+/*
+ * Fast implementation of an empty collection
+ */
+internal class EmptyCollection: ICollection, IEnumerator {
+
+    private static EmptyCollection s_theEmptyCollection = new EmptyCollection();
+
+    private EmptyCollection() { }
+
+    // Return the same instance all the time, since it's immutable
+    internal static EmptyCollection Instance { get { return s_theEmptyCollection; } }
+
+    // ICollection implementation
+    IEnumerator IEnumerable.GetEnumerator() { return this; }
+    public int Count { get { return 0; } }
+    bool ICollection.IsSynchronized { get { return true; } }
+    object ICollection.SyncRoot { get { return this; } }
+    public void CopyTo(Array array, int index) { }
+
+    // IEnumerator implementation
+    object IEnumerator.Current { get { return null; } }
+    bool IEnumerator.MoveNext() { return false; }
+    void IEnumerator.Reset() { }
+}
+
+}