public override void VerifyRenderingInServerForm(Control control)
    {

    }

    protected void btnExcel_Click(object sender, EventArgs e)
    {
        grvAcceptanceStatus.Columns[0].Visible = false;
        grvAcceptanceStatus.Columns[1].Visible = false;

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

        Response.Charset = "";

      //  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);

        grvAcceptanceStatus.RenderControl(htmlWrite);
        
        Response.Write(stringWrite.ToString());

        Response.End();

    }