RoutedEventHandler Delegate C#

The RoutedEventHandler delegate is used for any routed event that does not report event-specific information in the event data. There are many such routed events; prominent examples include Click and Loaded.

The most noteworthy difference between writing a handler for a routed event as opposed to a general common language runtime (CLR) event is that the sender of the event (the element where the handler is attached and invoked) cannot be considered to necessarily be the source of the event. The source is reported as a property in the event data (Source). A difference between sender and Source is the result of the event being routed to different elements, during the traversal of the routed event through an element tree.

You can use either sender or Source for an object reference if you are deliberately not interested in the routing behavior of a direct or bubbling routed event and you only intend to handle routed events on the elements where they are first raised. In this circumstance, sender and Source are the same object.

If you do intend to take advantage of the inherent features of routed events and write your handlers accordingly, the two most important properties of the event data that you will work with when writing event handlers are Source and Handled.

http://msdn.microsoft.com/en-us/library/system.windows.routedeventhandler.aspx