TreeGX control has built-in drag & drop support so you can re-order nodes without writing any code. However, this drag & drop support expects that DevComponents.Tree.Node type is part of drag data.

If you are accepting drag & drop from external applications, for example File Explorer, you cannot control whether drag data contains DevComponents.Tree.Node type. TreeGXDragDrop Sample Project that you can download shows how to integrate external drag & drop and leave internal built-in drag & drop working as well.

If you need to completely disable internal drag & drop handing in TreeGX control and write everything yourself simply set DragDropEnabled=false