Basically, when the object assigned to the payload is valid, the DropInfo event is raised with a status DropPossible. Once the mouse leaves the object, the same event fires with status DropImpossible. Furthermore, this status depends on the value of the QueryResult - whether it is true or false. You may take a look at our online documentation specifying the arguments available during DropInfo and DragInfo events.
Let me know if you need any further assistance.
the Telerik team
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