imported signalr 1.1.3 into NzbDrone.

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

@@ -0,0 +1,65 @@
+// Copyright (c) Microsoft Open Technologies, Inc. All rights reserved. See License.md in the project root for license information.
+
+using System.Collections.Generic;
+
+namespace Microsoft.AspNet.SignalR.Infrastructure
+{
+    internal class DiffSet<T>
+    {
+        private readonly HashSet<T> _items;
+        private readonly HashSet<T> _addedItems;
+        private readonly HashSet<T> _removedItems;
+
+        public DiffSet(IEnumerable<T> items)
+        {
+            _addedItems = new HashSet<T>();
+            _removedItems = new HashSet<T>();
+
+            _items = new HashSet<T>(items);
+        }
+
+        public bool Add(T item)
+        {
+            if (_items.Add(item))
+            {
+                if (!_removedItems.Remove(item))
+                {
+                    _addedItems.Add(item);
+                }
+                return true;
+            }
+            return false;
+        }
+
+        public bool Remove(T item)
+        {
+            if (_items.Remove(item))
+            {
+                if (!_addedItems.Remove(item))
+                {
+                    _removedItems.Add(item);
+                }
+                return true;
+            }
+            return false;
+        }
+
+        public bool Contains(T item)
+        {
+            return _items.Contains(item);
+        }
+
+        public ICollection<T> GetSnapshot()
+        {
+            return _items;
+        }
+
+        public bool DetectChanges()
+        {
+            bool anyChanges = _addedItems.Count > 0 || _removedItems.Count > 0;
+            _addedItems.Clear();
+            _removedItems.Clear();
+            return anyChanges;
+        }
+    }
+}