ปัญหาการใช้ AutoCompleteExtender กับ updatepanel ไม่ได้

 <asp:UpdatePanel ID="UpdatePanel1" runat="server">
                <contentTemplate>
...
...
...
 <asp:TextBox ID="TxOperator" runat="server" Font-Size="Medium" MaxLength="256"></asp:TextBox>
                <cc1:AutoCompleteExtender ID="AutoCompleteExtenderOPName" runat="server" 
                    CompletionListElementID="autocompleteDropDownPanel" FirstRowSelected="True" 
                    MinimumPrefixLength="0" ServiceMethod="FindEmployeeName" 
                    ServicePath="DORWebService.asmx" TargetControlID="TxOperator">
                </cc1:AutoCompleteExtender>
                <asp:Panel ID="autocompleteDropDownPanel" runat="server" Height="85px" 
                    ScrollBars="Vertical" />
...
...

      </contentTemplate>
                                      <Triggers>
                <asp:AsyncPostBackTrigger ControlID = "ddlLocal" EventName = "SelectedIndexChanged" />
                </Triggers>
                </asp:UpdatePanel>