I tested your code but I wasn't able to reproduce the behavior where the events doesn't fire. Can you please double check that you have set the IsDragDropEnabled property of the RadTreeView to true? I also attached a sample project, can you please give it a try and let me know if I am missing something?
As for forbidding drop on specific RadTreeViewItem you can set the item's IsDropAllowed
property to false. This property indicates whether the tree item can accept data that the user drags onto it.
In addition you can take a look at the Drag and Drop
and the Disable Drop at Specific Location
Please let me know if you need any further assistance.
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