[Solved] Excel file blank when exporting GridView to Excel in ASP.Net

hi,

i am trying to export a dynamically generated gridview to excel file,

on click an excel was generated but after opening the file there are only <div> tags inside the file,

my code is like below

<td>    
    <asp:Menu runat="server" ID="Export" Visible="false" DynamicHorizontalOffset="0"
        StaticMenuItemStyle-Height="24px" StaticMenuItemStyle-HorizontalPadding="4px"
        Orientation="Horizontal" StaticDisplayLevels="1" DynamicMenuItemStyle-VerticalPadding="4px"
        StaticEnableDefaultPopOutImage="false" OnMenuItemClick="Export_MenuItemClick">
        <StaticMenuItemStyle ForeColor="White" />
        <StaticMenuStyle CssClass="nav_main" />
        <DynamicHoverStyle CssClass="nav_main" ForeColor="White" />
        <DynamicMenuItemStyle CssClass="nav_main_hover" />
        <DynamicMenuItemStyle HorizontalPadding="3px" />
        <Items>                            
            <asp:MenuItem Target="_blank" Text="Excel"></asp:MenuItem>
            </asp:MenuItem>
        </Items>
    </asp:Menu>
</td>

 <div style="width:100%; overflow-y:scroll;height:500px " >
 <asp:Panel ID="pnlshpRpt" ClientIDMode="Static" runat="server" Visible="false" Width="99.4%" BorderStyle="Solid" BorderColor="Maroon">
 <center>

 <div id="divReport" style="overflow-y: auto; height:auto;">
 
 <asp:GridView ID="grdShipSummaryReport" runat="server" Width="99.3%" BorderColor="#CC3300" BorderStyle="Solid"
 CellPadding="2" HeaderStyle-CssClass="HeaderStyle" AlternatingRowStyle-CssClass="altItemStyle" RowStyle-CssClass="grid_row" OnDataBound="grdShipSummaryReport_DataBound">
 <AlternatingRowStyle CssClass="altItemStyle" />
 <HeaderStyle Font-Size="10 pt" CssClass="HeaderStyle" />
 <RowStyle Font-Size="11px" CssClass="ItemStyle" />
 </asp:GridView>

 code behind

        public override void VerifyRenderingInServerForm(Control control)
        {
            
        }

        protected void Export_MenuItemClick(object sender, MenuEventArgs e)
        {
                string Filename = "LPDPReport" + DateTime.Now + ".xls";
                Response.ClearContent();
                Response.Clear();
                Response.Buffer = true;
                Response.ClearHeaders();
                Response.Charset = "";
                Response.ContentType = "application/vnd.ms-excel";
                Response.AddHeader("Content-Disposition", "attachment;Filename=" + Filename);
                StringWriter str = new StringWriter();
                HtmlTextWriter htw = new HtmlTextWriter(str);
                Response.Cache.SetCacheability(HttpCacheability.NoCache);

                if (Convert.ToInt32(ddlShpRptType.SelectedValue.ToString()) != 22)
                {
                    grdShipSummaryReport.AllowPaging = false;
                    
                    grdShipSummaryReport.GridLines = GridLines.Both;
                    grdShipSummaryReport.HeaderStyle.Font.Bold = true;
                    grdShipSummaryReport.RenderControl(htw);
                    Response.Write(str.ToString());
                    Response.Flush();
                    Response.Close();
                    Response.End();
                }
                else
                {
                    grdlpdp.AllowPaging = false;
                    grdlpdp.GridLines = GridLines.Both;
                    grdlpdp.HeaderStyle.Font.Bold = true;
                    grdlpdp.RenderControl(htw); 
                    Response.Write(str.ToString());
                    Response.Flush();
                    Response.Close();
                    Response.End();

                }            
        }

can someone help to find my mistake and correct