I'm not sure if I understand correctly the requirements, however in order to start drag drop operation there should be a mouse interaction
with the desired element. Firstly you will need to set the attached telerik:DragDropManager.AllowDrag
property of the element in XAML and then to add DragInitialize handler in the code.
As for the DoDragDrop method - it comes from the framework itself and you don't need to use it as it is already implemented in the methods of the DragDropManager (you can check the Events
section of the DragDropManager online help documentation).
Hope this helps. If you have any further questions let us know.