Merge commit 'b78f6541dc5d8a32c3129960b3344dcedb8e5735' as 'NHotkey'

NHotkey/NHotkey.Wpf/WeakReferenceCollection.cs

@@ -0,0 +1,45 @@
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.Linq;
+
+namespace NHotkey.Wpf
+{
+    class WeakReferenceCollection<T> : IEnumerable<T>
+        where T : class
+    {
+        private readonly List<WeakReference> _references = new List<WeakReference>();
+        
+        public IEnumerator<T> GetEnumerator()
+        {
+            var references = _references.ToList();
+            foreach (var reference in references)
+            {
+                var target = reference.Target;
+                if (target != null)
+                    yield return (T) target;
+            }
+            Trim();
+        }
+
+        public void Add(T item)
+        {
+            _references.Add(new WeakReference(item));
+        }
+
+        public void Remove(T item)
+        {
+            _references.RemoveAll(r => (r.Target ?? item) == item);
+        }
+
+        public void Trim()
+        {
+            _references.RemoveAll(r => !r.IsAlive);
+        }
+
+        IEnumerator IEnumerable.GetEnumerator()
+        {
+            return GetEnumerator();
+        }
+    }
+}