--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Implab/Components/LazyAndWeak.cs	Wed Mar 23 19:51:45 2016 +0300
@@ -0,0 +1,44 @@
+using System;
+using System.Threading;
+
+namespace Implab.Components {
+    public class LazyAndWeak<T> where T : class {
+
+        readonly Func<T> m_factory;
+        readonly object m_lock;
+        WeakReference m_reference;
+
+
+        public LazyAndWeak(Func<T> factory, bool useLock) {
+            Safe.ArgumentNotNull(factory, "factory");
+            m_factory = factory;
+            m_lock = useLock ? new object() : null;
+        }
+
+        public LazyAndWeak(Func<T> factory) : this(factory, false) {
+        }
+
+        public T Value {
+            get {
+                while (true) {
+                    var weak = m_reference;
+                    T value;
+                    if (weak != null) {
+                        value = weak.Target as T;
+                        if (value != null)
+                            return value;
+                    }
+
+                    if (m_lock == null) {
+                        value = m_factory();
+
+                        if (Interlocked.CompareExchange(ref m_reference, new WeakReference(value), weak) == weak)
+                            return value;
+                    } else {
+                    }
+                }
+            }
+        }
+    }
+}
+