GanttView cancel drag under certain conditions

Hello, Blas,      

As a descendant of RadDragDropService, GanttViewDragDropService handles the whole drag and drop operation. Its PreviewDragOver event allows you to control on what targets the task being dragged can be dropped on. Here you can set the CanDrop property to false and thus the drop operation will be forbidden. The PreviewDragDrop event allows you to get a handle on all the aspects of the drag and drop operation, the source (drag) RadGanttView, the destination (target) control, as well as the task being dragged.

Additional information about the basic drag drop service and its derivative used in RadGanttView is available in the following help articles:

https://docs.telerik.com/devtools/winforms/telerik-presentation-framework/raddragdropservice

https://docs.telerik.com/devtools/winforms/controls/ganttview/drag-and-drop/ganttviewdragdropservice

I hope this information helps. If you need any further assistance please don't hesitate to contact me. 

Regards,
Dess | Tech Support Engineer, Sr.
Progress Telerik