Export GridView Data To Excel

private void ExportDynamicReportToExcel()
{
string attachment = "attachment; filename=File.xls";
Response.ClearContent();
Response.AddHeader("content-disposition", attachment);
Response.ContentType = "application/ms-excel";
StringWriter sw = new StringWriter();
HtmlTextWriter htw = new HtmlTextWriter(sw);

// Create a form to contain the grid
HtmlForm frm = new HtmlForm();
GridView1.Parent.Controls.Add(frm);
frm.Attributes["runat"] = "server";
frm.Controls.Add(GridView1);
frm.RenderControl(htw);
Response.Write(sw.ToString());
Response.End();
}