Imported Upstream version 4.0.0~alpha1

Former-commit-id: 806294f5ded97629b74c85c09952f2a74fe182d9

external/referencesource/System.ServiceModel/System/ServiceModel/Description/MessageDirection.cs

@@ -0,0 +1,24 @@
+//------------------------------------------------------------
+// Copyright (c) Microsoft Corporation.  All rights reserved.
+//------------------------------------------------------------
+namespace System.ServiceModel.Description
+{
+    public enum MessageDirection
+    {
+        Input,
+        Output
+    }
+
+    static class MessageDirectionHelper
+    {
+        internal static bool IsDefined(MessageDirection value)
+        {
+            return (value == MessageDirection.Input || value == MessageDirection.Output);
+        }
+
+        internal static MessageDirection Opposite(MessageDirection d)
+        {
+            return d == MessageDirection.Input ? MessageDirection.Output : MessageDirection.Input;
+        }
+    }
+}