Imported Upstream version 4.0.0~alpha1

Former-commit-id: 806294f5ded97629b74c85c09952f2a74fe182d9

external/referencesource/System.ServiceModel/System/Collections/ObjectModel/FreezableCollection.cs

@@ -0,0 +1,78 @@
+//----------------------------------------------------------------
+// Copyright (c) Microsoft Corporation.  All rights reserved.
+//----------------------------------------------------------------
+
+namespace System.Collections.ObjectModel
+{
+    using System;
+    using System.Collections.Generic;
+    using System.ServiceModel;
+
+    class FreezableCollection<T> : Collection<T>, ICollection<T>
+    {
+        bool frozen;
+
+        public FreezableCollection()
+            : base()
+        {
+        }
+
+        public FreezableCollection(IList<T> list)
+            : base(list)
+        {
+        }
+
+        public bool IsFrozen
+        {
+            get
+            {
+                return this.frozen;
+            }
+        }
+
+        bool ICollection<T>.IsReadOnly
+        {
+            get
+            {
+                return this.frozen;
+            }
+        }
+
+        public void Freeze()
+        {
+            this.frozen = true;
+        }
+
+        protected override void ClearItems()
+        {
+            ThrowIfFrozen();
+            base.ClearItems();
+        }
+
+        protected override void InsertItem(int index, T item)
+        {
+            ThrowIfFrozen();
+            base.InsertItem(index, item);
+        }
+
+        protected override void RemoveItem(int index)
+        {
+            ThrowIfFrozen();
+            base.RemoveItem(index);
+        }
+
+        protected override void SetItem(int index, T item)
+        {
+            ThrowIfFrozen();
+            base.SetItem(index, item);
+        }
+
+        void ThrowIfFrozen()
+        {
+            if (this.frozen)
+            {
+                throw DiagnosticUtility.ExceptionUtility.ThrowHelperError(new InvalidOperationException(SR.ObjectIsReadOnly));
+            }
+        }
+    }
+}