Look at this drag and drop sample:

http://www.eggheadcafe.com/tutorials/aspnet/847ac120-3cdc-4249-8029-26c15de209d1
/net-treeview-faq--drag.aspx

Instead of reacting to the events for drag, you just initiate the methods
to grab the selected node and then do something with it.  By default, it
you move the top node of a branch, all nodes under it will maintain
their reference to it when it is relocated.