lan Blackburn will show you how to make it possible to support dragging over any type of layout.
A common requirement for a rich UI in a business application is to support dragging and dropping of UI elements. For this to be successful you will need to be able to detect what elements you are dragging over, and you will need to support dragging over any type of layout (such as a complex grid layout), which is a contrast to many examples out there that only show dragging and dropping in relation to absolute layout with a Canvas.