imported signalr 1.1.3 into NzbDrone.

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

@@ -0,0 +1,43 @@
+// Copyright (c) Microsoft Open Technologies, Inc. All rights reserved. See License.md in the project root for license information.
+
+using System;
+using System.Threading;
+using System.Diagnostics.CodeAnalysis;
+
+namespace Microsoft.AspNet.SignalR.Infrastructure
+{
+    internal class DisposableAction : IDisposable
+    {
+        [SuppressMessage("Microsoft.Performance", "CA1823:AvoidUnusedPrivateFields", Justification = "The client projects use this.")]
+        public static readonly DisposableAction Empty = new DisposableAction(() => { });
+
+        private Action<object> _action;
+        private readonly object _state;
+
+        public DisposableAction(Action action)
+            : this(state => ((Action)state).Invoke(), state: action)
+        {
+
+        }
+
+        public DisposableAction(Action<object> action, object state)
+        {
+            _action = action;
+            _state = state;
+        }
+
+        protected virtual void Dispose(bool disposing)
+        {
+            if (disposing)
+            {
+                Interlocked.Exchange(ref _action, (state) => { }).Invoke(_state);
+            }
+        }
+
+        public void Dispose()
+        {
+            Dispose(true);
+        }
+    }
+
+}