GridView中数据导入Excel中，这个代码哪有问题？？？

这段代码产生的结果是一个Excel里面一堆代码，问题出在哪啊？？？？？
  private void Export(string FileType, string FileName)
    {
       
        string filename = "WorkHoursReport.csv";
        Response.Clear();
        Response.Charset = "GB2312";
        Response.Buffer = true;
        Response.ContentEncoding = System.Text.Encoding.GetEncoding("GB2312");
        Response.AddHeader("Content-Disposition", "attachment;filename=" + HttpUtility.UrlEncode(filename, System.Text.Encoding.UTF8).ToString());
        Response.ContentType = FileType;
        this.EnableViewState = false;
        StringWriter tw = new StringWriter();
        HtmlTextWriter hw = new HtmlTextWriter(tw);
        GridView1.RenderControl(hw);
        Response.Write(tw.ToString());
        Response.End();
    }    protected void bt_export_Click(object sender, EventArgs e)
    {
        Export("application/ms-excel", "WorkHoursReport.xls");
    }
    public override void VerifyRenderingInServerForm(Control control)
    {    }