How to put Header in Excel Report.....Im exporting Excel sheet from C#

protected void btnExcel_Click1(object sender, ImageClickEventArgs e)
{
    Response.Clear();
    Response.AddHeader("Content-Disposition", "attachment;filename=AttandanceReport.xls");
    Response.Charset = "";
    Response.ContentType = "application/vnd.xls";
    System.IO.StringWriter stringWrite = new System.IO.StringWriter();
    System.Web.UI.HtmlTextWriter htmlWrite = new HtmlTextWriter(stringWrite);
    // grdreport1.BorderStyle = BorderStyle.Solid;
    // grdreport1.BorderWidth = 1;
    //   grdreport1.BackColor = Color.WhiteSmoke;
    // grdreport1.GridLines = GridLines.Both;
    grdreport1.Font.Name = "Verdana";
    grdreport1.Font.Size = FontUnit.XXSmall;
    // grdreport1.HeaderStyle.BackColor = Color.DimGray;
    // grdreport1.HeaderStyle.ForeColor = Color.White;
    grdreport1.RowStyle.HorizontalAlign = HorizontalAlign.Center;
    grdreport1.RowStyle.VerticalAlign = VerticalAlign.Top;
    grdreport1.RenderControl(htmlWrite);
    Response.Write(stringWrite.ToString());
    Response.End();
}