This calls Northwoods.GoXam.PartManager.CopyParts to create an Northwoods.GoXam.Model.IDataCollection which is passed to DoDragDrop to actually start the drag-and-drop process.

If the result of the call to DoDragDrop returns DragDropEffects.None, this just cancels the operation of this dragging tool. If the result is DragDropEffects.Move and the data was moved to a different diagram, this will delete the original DraggedParts. Otherwise (if the result was a copy) this will move the dragged parts back to their original locations. Finally this stops this tool.

Reference

DraggingTool Class
DraggingTool Members