C#使用数据流导出DataGrid数据

    public void ExportExcelNew(DataGrid dg)
    {
        string fileName = chapterList.SelectedItem.Text;
        string str = fileName + ".xls";
        HttpContext.Current.Response.Clear();
        HttpContext.Current.Response.AppendHeader("Content-Disposition", "attachment;filename=" +

        HttpUtility.UrlPathEncode(str));
        HttpContext.Current.Response.ContentEncoding = Encoding.GetEncoding("GB2312");
        HttpContext.Current.Response.Charset = "";
        HttpContext.Current.Response.ContentType = "application/vnd.ms-excel";
        System.Text.StringBuilder sb = new System.Text.StringBuilder();
        StringWriter writer = new StringWriter(sb);
        HtmlTextWriter writer2 = new HtmlTextWriter(writer);
        dg.RenderControl(writer2);
        writer2.Close();
        writer.Close();
        HttpContext.Current.Response.Write("<meta http-equiv=\"content-type\" content=\"application/ms-excel; charset = gb2312\"/>");
        HttpContext.Current.Response.Write(sb.ToString());
        HttpContext.Current.Response.End();
    }