WebTreeView from WebListBox?

I wanted to implement a WebTreeView from a WebListBox.
So I created a WebListBox Control on my web page.
I created a class called WebTreeView that inherits from WebListBox.
I changed the subclass of the WebListBox on the web page to WebTreeView.

Why didn’t my webTreeView show up in the Library?

Should I have started with a WebControl rather than a WebListBox?