How to do Up and Down navigation in Tree view?

Question

I have a TreeView structure where i wanna do move up and move down navigation.How can i do the same.
I am storing the same the tree view structure designed in xml file.
when ever the up and down navigation is done in the existing structure the same tree view structure should be saved back to the xml file.
how can i do the same? 


actually i am able to do the move up navigation but not the move down. But the move up navigation also when ever i save it to xml file it is not not reflected in the xml file.

Similarly i also wanna know how to know how to do drag and drop.
Also when ever i edit name of the existing tree view design then it is throwing an exception.
I think this is because i have edited the name with which i am trying to excess that treeview structure from the xml. so it is throwing an exception. How to over come the same. And the update i do in the name of the tree view should reflect back in the xml again for drag and drop as well as tree view structure name edit also.