The callback function of a routed event has the second parameter e of type RoutedEventArgs or its inheritor. The Source property of this parameter holds reference to the object that raised the event. In contrast to that the sender parameter holds reference to the object where the event handler was invoked.
C#
void RoutedEventRaised( object sender, RoutedEventArgs e )
{
object source = e.Source;
}
That's it!