imported signalr 1.1.3 into NzbDrone.

src/Microsoft.AspNet.SignalR.Core/Infrastructure/Disposer.cs

@@ -0,0 +1,62 @@
+// Copyright (c) Microsoft Open Technologies, Inc. All rights reserved. See License.md in the project root for license information.
+
+using System;
+using System.Diagnostics;
+using System.Diagnostics.CodeAnalysis;
+using System.Threading;
+
+namespace Microsoft.AspNet.SignalR.Infrastructure
+{
+    /// <summary>
+    /// Helper class to manage disposing a resource at an arbirtary time
+    /// </summary>
+    internal class Disposer : IDisposable
+    {
+        private static readonly object _disposedSentinel = new object();
+
+        private object _disposable;
+
+        public void Set(IDisposable disposable)
+        {
+            if (disposable == null)
+            {
+                throw new ArgumentNullException("disposable");
+            }
+
+            object originalFieldValue = Interlocked.CompareExchange(ref _disposable, disposable, null);
+            if (originalFieldValue == null)
+            {
+                // this is the first call to Set() and Dispose() hasn't yet been called; do nothing
+            }
+            else if (originalFieldValue == _disposedSentinel)
+            {
+                // Dispose() has already been called, so we need to dispose of the object that was just added
+                disposable.Dispose();
+            }
+            else
+            {
+#if !NET35 && !SILVERLIGHT && !NETFX_CORE
+                // Set has been called multiple times, fail
+                Debug.Fail("Multiple calls to Disposer.Set(IDisposable) without calling Disposer.Dispose()");
+#endif
+            }
+        }
+
+        protected virtual void Dispose(bool disposing)
+        {
+            if (disposing)
+            {
+                var disposable = Interlocked.Exchange(ref _disposable, _disposedSentinel) as IDisposable;
+                if (disposable != null)
+                {
+                    disposable.Dispose();
+                }
+            }
+        }
+
+        public void Dispose()
+        {
+            Dispose(true);
+        }
+    }
+}