1 files changed, 76 insertions, 0 deletions

diff --git a/Rx.NET/System.Reactive.Linq/Reactive/Linq/Observαble/Defer.cs b/Rx.NET/System.Reactive.Linq/Reactive/Linq/Observαble/Defer.cs
new file mode 100644
index 0000000..ba3dcc4
--- /dev/null
+++ b/Rx.NET/System.Reactive.Linq/Reactive/Linq/Observαble/Defer.cs
@@ -0,0 +1,76 @@
+// Copyright (c) Microsoft Open Technologies, Inc. All rights reserved. See License.txt in the project root for license information.
+
+#if !NO_PERF
+using System;
+using System.Reactive.Disposables;
+
+namespace System.Reactive.Linq.Observαble
+{
+    class Defer<TValue> : Producer<TValue>, IEvaluatableObservable<TValue>
+    {
+        private readonly Func<IObservable<TValue>> _observableFactory;
+
+        public Defer(Func<IObservable<TValue>> observableFactory)
+        {
+            _observableFactory = observableFactory;
+        }
+
+        protected override IDisposable Run(IObserver<TValue> observer, IDisposable cancel, Action<IDisposable> setSink)
+        {
+            var sink = new _(this, observer, cancel);
+            setSink(sink);
+            return sink.Run();
+        }
+
+        public IObservable<TValue> Eval()
+        {
+            return _observableFactory();
+        }
+
+        class _ : Sink<TValue>, IObserver<TValue>
+        {
+            private readonly Defer<TValue> _parent;
+
+            public _(Defer<TValue> parent, IObserver<TValue> observer, IDisposable cancel)
+                : base(observer, cancel)
+            {
+                _parent = parent;
+            }
+
+            public IDisposable Run()
+            {
+                var result = default(IObservable<TValue>);
+                try
+                {
+                    result = _parent.Eval();
+                }
+                catch (Exception exception)
+                {
+                    base._observer.OnError(exception);
+                    base.Dispose();
+                    return Disposable.Empty;
+                }
+
+                return result.SubscribeSafe(this);
+            }
+
+            public void OnNext(TValue value)
+            {
+                base._observer.OnNext(value);
+            }
+
+            public void OnError(Exception error)
+            {
+                base._observer.OnError(error);
+                base.Dispose();
+            }
+
+            public void OnCompleted()
+            {
+                base._observer.OnCompleted();
+                base.Dispose();
+            }
+        }
+    }
+}
+#endif
\ No newline at end of file