下载管理器启动后，HttpContext.Current.Response写入文件

    // LINE1: Add the file name and attachment, which will force the open/cance/save dialog to show, to the header
    HttpContext.Current.Response.AddHeader("Content-Disposition", "attachment; filename="Jpeg Package " 
                                            + DateTime.Now.ToString("MM-dd-yyyy hh-mm-ss") + ".zip"");

    // Add the file size into the response header
    //HttpContext.Current.Response.AddHeader("Content-Length", file.Length.ToString());

    // Set the ContentType
    HttpContext.Current.Response.ContentType = ReturnHttpContentType("download.zip");

    ZipOutputStream oZipStream = 
                   new ZipOutputStream(HttpContext.Current.Response.OutputStream);

    try
    {
        foreach (string file in files)
        {


            FileInfo fInfo = new FileInfo(file);
            ZipEntry oZipEntry = new ZipEntry(fInfo.Name);
            oZipStream.PutNextEntry(oZipEntry);
            byte[] buffer = File.ReadAllBytes(file);
            oZipStream.Write(buffer, 0, buffer.Length);

            //oZipStream.Flush();
        }
    }
    catch (Exception ex)
    {
        throw ex;
    }
    finally
    {
        oZipStream.Finish();
        oZipStream.Close();
        oZipStream.Dispose();

     }
     HttpContext.Current.Response.OutputStream.Flush();
     HttpContext.Current.Response.End();
}