asp.net 多个文件同时下载

 ckl_ck.Items.Clear();
        DirectoryInfo TheFolder = new DirectoryInfo(Server.MapPath("Resource/Help"));
        //遍历文件夹下的文件
        foreach (FileInfo NextFile in TheFolder.GetFiles())
            this.ckl_ck.Items.Add(NextFile.Name);

 protected void Btn_down_Click(object sender, EventArgs e)
    {
        if (ckl_ck.Items.Count > 0)
        {
            List<string> listFJ = new List<string>();//保存附件路径
            List<string> listFJName = new List<string>();//保存附件名字
            for (int i = 0; i < ckl_ck.Items.Count; i++)
            {
                if (ckl_ck.Items[i].Selected)
                {
                    listFJ.Add(Server.MapPath("Resource/Help/") + ckl_ck.Items[i].Text);
                    listFJName.Add(ckl_ck.Items[i].Text);
                }

            }
            string time = DateTime.Now.Ticks.ToString();
            ZipFileMain(listFJ.ToArray(), listFJName.ToArray(), Server.MapPath("Resource/Help/" + time + ".zip"), 9);//压缩文件
            DownloadFile(Server.UrlEncode("附件.zip"), Server.MapPath("Resource/Help/" + time + ".zip"));//下载文件
        }
    }
    private void DownloadFile(string fileName, string filePath)
    {
        FileInfo fileInfo = new FileInfo(filePath);
        Response.Clear();
        Response.ClearContent();
        Response.ClearHeaders();
        Response.AddHeader("Content-Disposition", "attachment;filename=" + fileName);
        Response.AddHeader("Content-Length", fileInfo.Length.ToString());
        Response.AddHeader("Content-Transfer-Encoding", "binary");
        Response.ContentType = "application/octet-stream";
        Response.ContentEncoding = System.Text.Encoding.GetEncoding("gb2312");
        Response.WriteFile(fileInfo.FullName);
        Response.Flush();
        File.Delete(filePath);//删除已下载文件
        Response.End();
    }

    /// <summary>
    /// 压缩文件
    /// </summary>
    /// <param name="fileName">要压缩的所有文件（完全路径)</param>
    /// <param name="fileName">文件名称</param>
    /// <param name="name">压缩后文件路径</param>
    /// <param name="Level">压缩级别</param>
    public void ZipFileMain(string[] filenames, string[] fileName, string name, int Level)
    {
        ZipOutputStream s = new ZipOutputStream(File.Create(name));
        Crc32 crc = new Crc32();
        //压缩级别
        s.SetLevel(Level); // 0 - store only to 9 - means best compression
        try
        {
            int m = 0;
            foreach (string file in filenames)
            {
                //打开压缩文件
                FileStream fs = File.OpenRead(file);//文件地址
                byte[] buffer = new byte[fs.Length];
                fs.Read(buffer, 0, buffer.Length);
                //建立压缩实体
                ZipEntry entry = new ZipEntry(fileName[m].ToString());//原文件名
                //时间
                entry.DateTime = DateTime.Now;
                //空间大小
                entry.Size = fs.Length;
                fs.Close();
                crc.Reset();
                crc.Update(buffer);
                entry.Crc = crc.Value;
                s.PutNextEntry(entry);
                s.Write(buffer, 0, buffer.Length);
                m++;
            }
        }
        catch
        {
            throw;
        }
        finally
        {
            s.Finish();
            s.Close();
        }
    }