AJAX ServiceReference Error

 Type 'System.Web.UI.ServiceReference' does not have a public property named 'UpdatePanel'.
 I'm getting some errors trying to implement an ajax page.

Can someone tell me why I would get this?
I'm new to using ajax so I'm not sure what I am missing. 
I have a ScriptManager on the page with a service Reference. 
 
<asp:ScriptManager id="script1" runat="server">
         <Services>
           <asp:ServiceReference Path="AutoComplete.asmx">
         
         </Services>
       </asp:ScriptManager>
<asp:UpdatePanel id="UpdatePanel1" runat="server">
   &n ...