 <p>Here is a great article on the subject <a href="http://www.codeproject.com/KB/ajax/autosuggestextender.aspx" rel="nofollow noreferrer">http://www.codeproject.com/KB/ajax/autosuggestextender.aspx</a></p> <p>I've also written a follow-up article explaining how to call an asynchronous server side auto post back event on a user's selection: <a href="http://www.codeproject.com/KB/webforms/PostbackAutoCompleteExten.aspx" rel="nofollow noreferrer">http://www.codeproject.com/KB/webforms/PostbackAutoCompleteExten.aspx</a></p>