if (!Directory.Exists(Server.MapPath("UserTemp")))
            {
                Directory.CreateDirectory(Server.MapPath("UserTemp"));
            }
            string path = Path.Combine("UserTemp//", "白名单导出_" + DateTime.Now.ToString("yyyyMMddHHmmss") + ".txt");
            string str5 = base.Server.MapPath(path);

            if (File.Exists(str5))
            {
                File.Delete(str5);
            }
            //数据量大用另外一种方法
            FileInfo file = new FileInfo(str5);//用于获取文件信息
            StreamWriter textFile = null;
            textFile = file.CreateText();


            string sqlWhile = "SELECT WMobile FROM WMobile";
            DataTable tab = new DataTable();
            tab = DBCommonClass.DbAccessHelper.ExecuteDataTable(new DbCommandData(sqlWhile));
            string strWhile = string.Empty;
            for (int i = 0; i < tab.Rows.Count; i++)
            {
                string str = tab.Rows[i][0].ToString();
                strWhile += str + "\r\n";
            }

            textFile.Write(strWhile);
            textFile.Close();

///////////////////////////////////////////////////下面就是下载代码了
            //Response.Clear();//清空输出
            //Response.Charset = "GB2312";//设定编码
            //Response.ContentEncoding = System.Text.Encoding.UTF8;
            //Response.AddHeader("Content-Disposition", "attachment;filename=" + Server.UrlEncode(file.Name));
            //Response.AddHeader("Content-length", file.Length.ToString());
            //Response.ContentType = "application/octet-stream";
            ////ms-txt";
            //Response.WriteFile(file.FullName);
            //Response.End();
            Response.Clear();
            Response.ClearContent();
            Response.ClearHeaders();
            Response.AddHeader("Content-Disposition", "attachment;filename=" + HttpUtility.UrlEncode(file.Name, Encoding.UTF8));
            Response.AddHeader("Content-Length", file.Length.ToString());
            Response.AddHeader("Content-Transfer-Encoding", "binary");
            Response.ContentType = "application/octet-stream";
            Response.ContentEncoding = System.Text.Encoding.GetEncoding("gb2312");
            Response.WriteFile(file.FullName);
            Response.Flush();
            HttpContext.Current.ApplicationInstance.CompleteRequest();