Creating A Custom Tree View In ASPX

I've created a basic table in SQL,

ID, Foldername, ParentID, parentLevel
1, Domestic, 0,0
2, commercial, 0,0
3, Product, 1,1
4, product, 1,1
5, Item, 3,2
6, product, 2,1
7, item, 6,2

I've created a basic web page to that drills down level by level. that all works fine.

I want to manage this table now in an admin page, and was looking for some kind of tree view type code that will allow a user to expand a level and drill down to sub levels.

Code:
Private Sub LoadList()
Litlist.Text = ""
Litlist.Text += "<tr style='background:#808080; color:white; text-align:center'>"
Litlist.Text += "<td>ID</td>"
Litlist.Text += "<td>Name</td>"

[Code] ....

This kinda works but doesn't allow me to expand to create have a collapsible tree view or show/hide TR's. How to do this using a simple table like I have for multiple levels.