Excel DownLoad

protected void lbtnDownloadReport_Click(object sender, EventArgs e)
    {
        GridView gv = new GridView();
        gv = Gridview1;
        gv.FooterRow.Visible = false;
        Download_Excel(gv, "Report.xls");

    }
    public void Download_Excel(GridView gv, string fileName)
    {

        HtmlForm form = new HtmlForm();

        string attachment = "attachment; filename=" + fileName + ".xls";

        Response.ClearContent();

        Response.AddHeader("content-disposition", attachment);

        Response.ContentType = "application/ms-excel";

        StringWriter stw = new StringWriter();

        HtmlTextWriter htextw = new HtmlTextWriter(stw);

        form.Controls.Add(gv);

        this.Controls.Add(form);
        form.RenderControl(htextw);

        Response.Write(stw.ToString());

        Response.End();


    }