How To Export Gridview Inside Update Panel to Excel

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C#

Hello All
I Want to export the gridview data to excel for that i have done this code is working properly without updatepanel

public override void VerifyRenderingInServerForm(Control control)
       {

       }

try
           {

               Response.Buffer = true;
               Response.AddHeader("content-disposition", string.Format("attachment; filename={0}", "Customers.xls"));
               Response.ContentType = "application/ms-excel";
               StringWriter sw = new StringWriter();
               HtmlTextWriter htw = new HtmlTextWriter(sw);
               gv_forms.AllowPaging = false;
               SearchBlank();
               //gv_forms.DataBind();
               //Change the Header Row back to white color
               gv_forms.HeaderRow.Style.Add("background-color", "#FFFFFF");
               //Applying stlye to gridview header cells
               for (int i = 0; i < gv_forms.HeaderRow.Cells.Count; i++)
               {
                   gv_forms.HeaderRow.Cells[i].Style.Add("background-color", "#507CD1");
               }
               int j = 1;
               //This loop is used to apply stlye to cells based on particular row
               foreach (GridViewRow gvrow in gv_forms.Rows)
               {
                   gvrow.BackColor = Color.White;
                   if (j <= gv_forms.Rows.Count)
                   {
                       if (j % 2 != 0)
                       {
                           for (int k = 0; k < gvrow.Cells.Count; k++)
                           {
                               gvrow.Cells[k].Style.Add("background-color", "#EFF3FB");
                           }
                       }
                   }
                   j++;
               }
               CheckBox ItemAll = (CheckBox)Convert.ChangeType((gv_forms.HeaderRow.FindControl("chk_all")), typeof(CheckBox));
               ItemAll.Visible = false;
               foreach (GridViewRow row in gv_forms.Rows)
               {
                   LinkButton lbtnview = (LinkButton)row.FindControl("lbtn_Edit");
                   LinkButton lbtnedit = (LinkButton)row.FindControl("LinkButton2");
                   CheckBox Item = (CheckBox)row.FindControl("chk_item");

                   lbtnview.Visible = false;
                   lbtnedit.Visible = false;
                   Item.Visible = false;

                   gv_forms.Columns[0].Visible = false;
                   gv_forms.Columns[5].Visible = false;
                   gv_forms.Columns[6].Visible = false;

               }
               gv_forms.RenderControl(htw);
               Response.Write(sw.ToString());
               Response.End();
           }
           catch { }

this code is working properly without update panel.
bet when we use update panel(Grid view inside the update panel)then it is not working plz help me
Thanks In Advance.