Programmatically Adding User Controls Inside An UpdatePanel

I’m having trouble dynamically adding controls inside an update panel with partial postbacks. I’ve read many articles on dynamic controls and I understand how to add and maintain them with postbacks but most of that information doesn’t apply and won’t work for partial postbacks. I can’t find any useful information about adding and maintaining them with UpdatePanels. I’d like to do this without creating a web service if it’s possible. Does anyone have any ideas or references to some helpful information?