A good performance Treeview using ajax

I have a requirement of a tree view with a very performance.i decided to build it with ajax so

What approach is better ie use a .net treeview control in updatepanel

OR

make a ajax call on clicking on each node

i know the 2nd oneis good but i need some more facts like if i used ist one and when anode clicked event is generated then whole tree view is posted but insecond one there is on demand loading

please send some more views

thanks

I have had some trouble with the treeview holding state inside an update panel, so if you can impliment it using ajax calls would be my recommendation.

-Alan