treeview sort

want my treeview to show in descending order.
using file and folder system to show files in treeview.

treeview1.sort does not even show. there is no class called sort.

   Dim rootDir As New DirectoryInfo(Server.MapPath("~//"))

            ' Enter the RecurseNodes function to recursively walk the directory tree.
            Dim RootNode As TreeNode = RecurseNodes(rootDir)
            ' Add this Node hierarchy to the TreeNode control.
            Treeview1.Nodes.Add(RootNode)