What'sthe reason you're using User Controls in a foreach loop? Why not simply use something like a ListView to present each item?
Using a UC is not a bad practice per se, but you'll run into all kinds of problems including state (you'll need to recreate the tree after a postback for example).
>> Why does the Delete button not respond correctly?
Don't know. I am not allowed to use my psychic skills here so it'll be impossible to say anything useful without seeing relevant code ;--)
Finally, since this is not related to my book, can we continue this discussion in a general ASP.NET cateogy: http://p2p.wrox.com/asp-net-4-539/