如何在WPF中检测不在目标上但在源上的丢弃？

I have a UserControl in my application which is stacked in a StackPanel. I want to undock the UserControl from the StackPanel via Drag&Drop and drop it somewhere else in my application. This works fine as long as I can intercept the DragOver, DragEnter,... events but when I drag my UserControl outside my application/window I get a "not possible" cursor.I have a UserControl in my application which is