// Create an observable for MouseLeftButtonDown
var mouseEvents = Observable.FromEvent<MouseButtonEventArgs> (mycontrol, "MouseLeftButtonDown");

//Query the observable just to select the points
var points = from ev in mouseEvents
                    select ev.EventArgs.GetPosition(this);

//Show points in windows title when ever user presses the left mouse button
points.Subscribe(p => this.Title = "Location = " + p.X + ", " + p.Y);