Repeater not working with export to excel

Question

<asp:Button ID="btnExport" runat="server" Text="Export" OnClick = "ExportToExcel" />

this is my button to export

protected void ExportToExcel(object sender, EventArgs e)
    {
        Response.Clear();
        Response.Buffer = true;
        Response.AddHeader("content-disposition", "attachment;filename=RepeaterExport.xls");
        Response.ContentEncoding = System.Text.Encoding.UTF8;
        Response.Charset = "UTF-8";
        Response.ContentType = "application/vnd.ms-excel.12";
        StringWriter sw = new StringWriter();
        HtmlTextWriter hw = new HtmlTextWriter(sw);
        rpt1.RenderControl(hw);
        Response.Write("<table>");
        Response.Write(sw.ToString());
        Response.Write("</table>");
        Response.Flush();
        Response.End();
    }

this is my code behind button but it is not working anything.