asp.net 下载的 问题

代码执行完毕后，页面中没有下载提示； 求解datetable  doclist=。。  
调用ExportToExcel.ExportExcel(Page, doclist, "规范文件", "规范文件");        /// <summary>
        /// 构建TABLE加上头
        /// </summary>
        /// <param name="page"></param>
        /// <param name="dtExcel"></param>
        /// <param name="strFileName"></param>
        public static void ExportExcel(System.Web.UI.Page page, System.Data.DataTable dtExcel, string head, string strFileName)
        {
            string strExtFile = strFileName.Trim();
            if (strExtFile.Substring(strExtFile.Length - 4, 4).ToUpper() != ".xls")
            {
                strExtFile += ".xls";
            }
            page.Response.Clear();
            page.Response.Buffer = true;
            page.Response.Charset = "utf-8";
            page.Response.ContentEncoding = System.Text.Encoding.GetEncoding("utf-8");
            page.Response.AppendHeader("Content-Disposition", "attachment;filename=" + System.Web.HttpUtility.UrlEncode(strExtFile, System.Text.Encoding.UTF8));
            page.Response.ContentType = "application/vnd.ms-excel";
            page.Response.Charset = "";
            page.EnableViewState = false;
            StringWriter stringWrite = new StringWriter();
            HtmlTextWriter htmlTxtWrite = new HtmlTextWriter(stringWrite);
            htmlTxtWrite.Write("<html>\r\n<meta content=\"text/html;charset=utf-8\"></meta>\r\n<body>\r\n");
            htmlTxtWrite.Write("<table cellspacing=\"0\" border=\"1\">\r\n");
            htmlTxtWrite.Write(head);
            htmlTxtWrite.Write("<tr>\r\n");
            for (int i = 0; i < dtExcel.Columns.Count; i++)
            {
                string strTitle = ConvertToHtmlCode(dtExcel.Columns[i].Caption.Trim());
                htmlTxtWrite.Write("\t<td bgcolor=\"lightblue\">" + strTitle + "</td>\r\n");
            }
            htmlTxtWrite.Write("</tr>\r\n");
            foreach (DataRow dr in dtExcel.Rows)
            {
                htmlTxtWrite.Write("<tr>\r\n");
                for (int i = 0; i < dtExcel.Columns.Count; i++)
                {
                    string strValue = "";
                    if (dtExcel.Columns[i].DataType == typeof(System.DateTime))
                    {
                        strValue = DateTimeConvertToString(dr[i]);
                    }
                    else
                    {
                        strValue = ConvertToHtmlCode(dr[i].ToString().Trim());
                    }
                    htmlTxtWrite.Write("\t<td>" + strValue + "</td>\r\n");
                }
                htmlTxtWrite.Write("</tr>\r\n");
            }
            htmlTxtWrite.Write("\r\n</table>\r\n</body>\r\n</html>");
            page.Response.Write(stringWrite.ToString());
            page.Response.End();
        }
界面中有updatepanel，打包下载，但打包下载有提示
输出 execle  的  ExportExcel方法之前好好的，   
更改了下调用，  
之前的  dataset doclist=。。 
      调用ExportToExcel.ExportExcel(Page, doclist.table[0], "规范文件", "规范文件");
求指点