Imported Upstream version 4.6.0.125

Former-commit-id: a2155e9bd80020e49e72e86c44da02a8ac0e57a4

mcs/class/referencesource/System.ServiceModel/System/ServiceModel/Channels/UnderstoodHeaders.cs

@@ -0,0 +1,58 @@
+//------------------------------------------------------------
+// Copyright (c) Microsoft Corporation.  All rights reserved.
+//------------------------------------------------------------
+namespace System.ServiceModel.Channels
+{
+    using System.Xml;
+    using System.ServiceModel;
+    using System.Collections;
+    using System.Collections.Generic;
+    using System.Collections.ObjectModel;
+    using System.Diagnostics;
+    using System.Runtime.Serialization;
+
+    public sealed class UnderstoodHeaders : IEnumerable<MessageHeaderInfo>
+    {
+        MessageHeaders messageHeaders;
+        bool modified;
+
+        internal UnderstoodHeaders(MessageHeaders messageHeaders, bool modified)
+        {
+            this.messageHeaders = messageHeaders;
+            this.modified = modified;
+        }
+
+        internal bool Modified
+        {
+            get { return modified; }
+            set { modified = value; }
+        }
+
+        public void Add(MessageHeaderInfo headerInfo)
+        {
+            messageHeaders.AddUnderstood(headerInfo);
+            modified = true;
+        }
+
+        public bool Contains(MessageHeaderInfo headerInfo)
+        {
+            return messageHeaders.IsUnderstood(headerInfo);
+        }
+
+        IEnumerator IEnumerable.GetEnumerator()
+        {
+            return this.GetEnumerator();
+        }
+
+        public IEnumerator<MessageHeaderInfo> GetEnumerator()
+        {
+            return messageHeaders.GetUnderstoodEnumerator();
+        }
+
+        public void Remove(MessageHeaderInfo headerInfo)
+        {
+            messageHeaders.RemoveUnderstood(headerInfo);
+            modified = true;
+        }
+    }
+}