AutoCompleteExtender in gridview

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C#

ASP.NET

I am working with autocompleteextender in gridview. I am getting key,value pair from webservice. When i am selecting item in textbox it is giving me the value which i got from webservice in alert. I need to assign this value to the hiddenfield which is in gridview. My code is as below. Can you please suggest me how can i do this?

<script type="text/javascript" language="javascript">
function GetCode(source, eventArgs) {
    alert(eventArgs.get_value());
}</script>


<asp:GridView ID="gvEmpworkhour" runat="server" AutoGenerateColumns="False" 
                ShowFooter="True" CellPadding="4" ForeColor="#333333" GridLines="None" 
                  onrowdatabound="gvEmpworkhour_RowDataBound" 
                  onrowcommand="gvEmpworkhour_RowCommand">
                <rowstyle backcolor="#EFF3FB" />
                <columns>
 <asp:TemplateField HeaderText="EmployeeName" HeaderStyle-HorizontalAlign="Center">
                        <itemtemplate>
                           
                             <asp:UpdatePanel ID="upEmployeeName" runat="server">
                             <contenttemplate>
                              <asp:AutoCompleteExtender ID="AutoCompleteExtender1" runat="server" MinimumPrefixLength="1" ServiceMethod="showEmployee"
                                ServicePath="~/WebService.asmx" TargetControlID="txtEmployeeName" CompletionInterval="1000" EnableCaching="true"
 CompletionSetCount="20" 
CompletionListCssClass="AutoExtender"
             CompletionListItemCssClass="AutoExtenderList"
             CompletionListHighlightedItemCssClass ="AutoExtenderHighlight"
             CompletionListElementID="divwidth" OnClientItemSelected="GetCode"> 
                            
                            <asp:TextBox ID="txtEmployeeName" runat="server" AutoPostBack="true" OnTextChanged="txtEmployeeName_TextChanged"> 
                            
                            <asp:HiddenField ID="hidEmpID" runat="server" />
                            </contenttemplate>
                            
                        </itemtemplate>                    
</columns>
               <footerstyle backcolor="#507CD1" font-bold="True" forecolor="White" />
               <pagerstyle backcolor="#2461BF" forecolor="White" horizontalalign="Center" />
               <SelectedRowStyle BackColor="#D1DDF1" Font-Bold="True" ForeColor="#333333" />
               <HeaderStyle BackColor="#507CD1" Font-Bold="True" ForeColor="White" />
               <editrowstyle backcolor="#2461BF" />
               <alternatingrowstyle backcolor="White" />