asp.net 2.0 how to persist node between page refresh

[andy]

I have made a webcontrol which i used to navigate through many
products.
My problem is that i need to retain the treeviews state after i refresh
the page

Every time i use navigate url to select a new product on the same page
the tree control refreshes, but am unsure how to get it to navigate
back to where it was. ( persist its state bewteen refreshes)

any ideas or articles,? ive been searching all day

cheers

andy