Export Gridview data to Excel

in click event, after the load event initiated:

Response.Clear();
Response.AddHeader("content-disposition", "attachment;filename=payment_details.xls");
Response.Charset = String.Empty;
 Response.ContentType = "application/ms-excel";
 StringWriter stringWriter = new StringWriter();
 HtmlTextWriter HtmlTextWriter = new HtmlTextWriter(stringWriter);
 grdPaymentDetl.RenderControl(HtmlTextWriter);
 Response.Write(stringWriter.ToString());
 Response.End();

add this method in aspx page:

public override void VerifyRenderingInServerForm(Control control)
 {
 /* Confirms that an HtmlForm control is rendered for the specified ASP.NET
 server control at run time. */
 }

Note: Do work Under <Updatapanel>