I can think of several reasons for this behavior:
1. The routed events do not reach the handlers.
Solution: Check that events are really not fired by adding a handler to the Source object or a Class handler for one of the base classes. Class handlers are added this way:
| new EventHandler<DragDropQueryEventArgs>(MyDelegate));
2. The destination is a part of a popup that is not part of the VisualTree, normally these popups will be created and opened in code.
Solution: Add these detached popups to the ParticipatingVisualRoots
collection during DragQuery.
3. Canvases with no background do not receive mouse events.
Solution: Assign a background (even Transparent) to these Canvases.
If these suggestions do not work for you, I will need more information:
Do you use nested drop targets?
Are you using Windows/Popups?
Anything specific in the VisualTree of the App? E.g. - overlays.
Ideally a sample project where this issue appears will help us get to the solution quickly.
the Telerik team
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