Export GridView To Excel

protected void Button1_Click(object sender, EventArgs e)
{
Response.AddHeader("content-disposition", "attachment;filename=FileName.xls");
Response.Charset = String.Empty;
Response.ContentType = "application/vnd.xls";
System.IO.StringWriter sw = new System.IO.StringWriter();
System.Web.UI.HtmlTextWriter hw = new HtmlTextWriter(sw);
GridView1.RenderControl(hw);
Response.Write(sw.ToString());
Response.End();
}
Source