I am sorry for the delayed reply, we were busy with the Beta 2 release of the controls which should be available for download now.
Unfortunately I cannot offer a workaround with the SP1 version of the controls (2009.2 812)
In the internal builds (and in the beta) the DragAndDropManager has the StartDrag() method and here is how you can use it:
1. Register for the MouseLeftButtonDown and Up events on the root visual (root page of your application). Use the rootPage.AddHandler(event, handler, true
); method to register for the event. This way you will be notified for the event even if is handled. This way you will know if the mouse is pressed or not.
2. Register for the MouseLeave event on the particular control
3. In the MouseLeave handler check if the mouse is pressed and start dragging using the StartDrag method on the DragAndDrop manager.
There really is no guarantee whether the mouse move event (and therefore the drag/drop events) will be called if the user moves the mouse quickly, so I cannot think of another workaround.
the Telerik team