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copied!<p>You can create Observables from existing events. You can use Observable.FromEvent for this purpose. You may write a GetMouseDown event wrapper like this, as an extension method for a UI Element.</p> <pre><code> public static IObservable<Event<MouseButtonEventArgs>> GetMouseDown (this UIElement el) { var allevents = Observable.FromEvent<MouseButtonEventHandler, MouseButtonEventArgs> ( h => new MouseButtonEventHandler(h), h => el.MouseDown += h, h=> el.MouseDown -= h ); return allevents; } </code></pre> <p>And later, you may 'handle' your event in a completely declarative manner. Like</p> <pre><code>//create an observable declaratively var mouseDowns=button.GetMouseDown(); //subcribe and do what ever you need mouseDowns.Subscribe(arg=> MessageBox.Show(arg.ClickCount.ToString()) ); </code></pre> <p>And here is how to create a 'drag' observable, with the intial position and current position.</p> <pre><code> //Get the initial position and dragged points using LINQ to Events var mouseDragPoints = from md in e.GetMouseDown() let startpos=md.EventArgs.GetPosition(e) from mm in e.GetMouseMove().Until(e.GetMouseUp()) select new { StartPos = startpos, CurrentPos = mm.EventArgs.GetPosition(e), }; //And subscribe here to mouseDragPoints </code></pre> <p>Read this article <a href="http://amazedsaint.blogspot.com/2009/11/linq-to-events-more-on-net-reactive.html" rel="nofollow noreferrer">LINQ to Events - More on .NET Reactive Extensions</a> and play with the source code.</p>

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