[System.Net.Http] Fix disposing of DelegatingHandler. Fixes #20818

mcs/class/System.Net.Http/System.Net.Http/DelegatingHandler.cs

@@ -34,6 +34,7 @@ namespace System.Net.Http
 	public abstract class DelegatingHandler : HttpMessageHandler
 	{
 		bool disposed;
+		HttpMessageHandler handler;
 		
 		protected DelegatingHandler ()
 		{
@@ -47,13 +48,24 @@ namespace System.Net.Http
 			InnerHandler = innerHandler;
 		}
 		
-		public HttpMessageHandler InnerHandler { get; set; }
+		public HttpMessageHandler InnerHandler {
+			get {
+				return handler;
+			}
+			set {
+				if (value == null)
+					throw new ArgumentNullException ("InnerHandler");
+
+				handler = value;
+			}
+		}
 		
 		protected override void Dispose (bool disposing)
 		{
 			if (disposing && !disposed) {
 				disposed = true;
-				InnerHandler.Dispose ();
+				if (InnerHandler != null)
+					InnerHandler.Dispose ();
 			}
 			
 			base.Dispose (disposing);

mcs/class/System.Net.Http/System.Net.Http_test.dll.sources

@@ -1,3 +1,4 @@
+System.Net.Http/DelegatingHandlerTest.cs
 System.Net.Http/ByteArrayContentTest.cs
 System.Net.Http/FormUrlEncodedContentTest.cs
 System.Net.Http/HttpClientHandlerTest.cs

mcs/class/System.Net.Http/Test/System.Net.Http/DelegatingHandlerTest.cs

@@ -0,0 +1,63 @@
+//
+// DelegatingHandlerTest.cs
+//
+// Authors:
+//	Marek Safar  <[email protected]>
+//
+// Copyright (C) 2014 Xamarin Inc (http://www.xamarin.com)
+//
+// Permission is hereby granted, free of charge, to any person obtaining
+// a copy of this software and associated documentation files (the
+// "Software"), to deal in the Software without restriction, including
+// without limitation the rights to use, copy, modify, merge, publish,
+// distribute, sublicense, and/or sell copies of the Software, and to
+// permit persons to whom the Software is furnished to do so, subject to
+// the following conditions:
+//
+// The above copyright notice and this permission notice shall be
+// included in all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+//
+
+using System;
+using NUnit.Framework;
+using System.Net.Http;
+using System.IO;
+using System.Threading.Tasks;
+
+namespace MonoTests.System.Net.Http
+{
+	[TestFixture]
+	public class DelegatingHandlerTest
+	{
+		class DefaultHandler : DelegatingHandler
+		{
+		}
+
+
+		[Test]
+		public void DisposeTest ()
+		{
+			var handler = new DefaultHandler ();
+			handler.Dispose ();
+		}
+
+		[Test]
+		public void InnerHandler_Invalid ()
+		{
+			var handler = new DefaultHandler ();
+			try {
+				handler.InnerHandler = null;
+				Assert.Fail ("#1");
+			} catch (ArgumentNullException) {
+			}
+		}
+	}
+}