I'm trying to get mouse cursor position when item droping in treeview.
I use DragOverTree event, but ExternalDragEventArgs always null.
DragOver event never rising.
In order to implement your scenario it is best to handle the RadDragAndDropManager.DragInfoEvent or RadDragAndDropManager.DropInfoEvent. Since the RadTreeView implementation internally uses the DragDropManager, all drag/drop related events of the manger will be triggered by the RadTreeView control.
The RadDragAndDropManager.DragInfoEvent can give you information about the drag in progress thus allowing you to track the CurrentDragPoint which you can access through the DragDropEventArgs. Or if you only need to get the CurrentDragPoint when a drop operation is complete then you can handle the RadDragAndDropManager.DropInfoEvent. In the event handler you can check if the status of the operation is DropComplete and then get the CurrentDragPoint coordinates.
You can attach event handlers to both events like so:
this.AddHandler(RadDragAndDropManager.DragInfoEvent, new EventHandler<DragDropEventArgs>(OnDragInfo));
this.AddHandler(RadDragAndDropManager.DropInfoEvent, new EventHandler<DragDropEventArgs>(OnDropInfo));
And then you can implement such a logic for getting the drag point coordinates: