// 生成100个测试txt文件
protected void Page_Load(object sender, EventArgs e)
        {
            for (var i = 1; i <= 100; i++)
            {
                using (StreamWriter writer = new StreamWriter(Server.MapPath("/Content/Txt/" +
                    i.ToString().PadLeft(3, '0') + ".txt"), false))
                {
                    writer.WriteLine(i.ToString().PadLeft(3,'0') + " - 这是测试的数据！");
                }
            }
            Response.Write("Create txt done");
        }

// 测试全并并下载
 protected void Page_Load(object sender, EventArgs e)
        {
            var dirInfos = Directory.GetFiles(Server.MapPath("/Content/Txt"));
            Response.ContentType = "application/octet-stream";
            Response.AppendHeader("Content-Disposition", "attachment;filename=" + HttpUtility.UrlEncode("all.txt", Encoding.UTF8));
            
            foreach (var str in dirInfos)
            {
                using (FileStream fs = new FileStream(str, FileMode.Open, FileAccess.Read))
                {
                    Byte[] bs = new Byte[fs.Length];
                    fs.Read(bs, 0, (int)fs.Length);
                    Response.BinaryWrite(bs);
                }

            }
            Response.End();
        }