export gridview into excel file

 public void excelgridview()

{

        Response.Clear();

        Response.AddHeader("content-disposition", "attachment; filename=FileName.xls");

        Response.Charset = "";

        // If you want the option to open the Excel file without saving than

        // comment out the line below

        // Response.Cache.SetCacheability(HttpCacheability.NoCache);

        Response.ContentType = "application/vnd.xls";

        System.IO.StringWriter stringWrite = new System.IO.StringWriter();

        System.Web.UI.HtmlTextWriter htmlWrite =
        new HtmlTextWriter(stringWrite);

        GridView1.RenderControl(htmlWrite);

        Response.Write(stringWrite.ToString());

        Response.End();

    }

    public override void VerifyRenderingInServerForm(System.Web.UI.Control control)
    {

        // Confirms that an HtmlForm control is rendered for the
        //  specified ASP.NET server control at run time.

    }

private void ExportToExcel(string strFileName, DataGrid dg)
{
Response.ClearContent();
Response.AddHeader("content-disposition", "attachment; filename=" + strFileName);
Response.ContentType = "application/excel";
System.IO.StringWriter sw = new System.IO.StringWriter();
HtmlTextWriter htw = new HtmlTextWriter(sw);
dg.RenderControl(htw);
Response.Write(sw.ToString());
Response.End();
}