Hi Hiroshi,
The explained scenario is a framework behavior - when the dragged item from the Windows Explorer enters the WPF application the default drag visual is changed to the default WPF one. And you won't be able to change the DragVisual in any of the methods of the DragDropManager. However you can check the approach demonstrated in
this blog post, which actually will help you to achieve the required - you will need to implement the library from example and use it with our DragDropManager.
Hope this will help you to achieve the required.
Regards,
Administrator
Telerik
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