C#通过URl批量下载&打包压缩

using ICSharpCode.SharpZipLib.Zip;

        public string DownloadFileByHttpUrl(List<string> HttpUrlList)
        {
            if (HttpUrlList == null || HttpUrlList.Count == 0)
            {
                return null;
            }
            try
            {
                var random = new Random();
                var zipMs = new MemoryStream();
                ZipOutputStream zipStream = new ZipOutputStream(zipMs);
                zipStream.SetLevel(9);//压缩率0~9
                foreach (var url in HttpUrlList)
                {
                    if (!string.IsNullOrWhiteSpace(url))
                    {
                        var urlStr = HttpUtility.UrlDecode(url);
                        Console.WriteLine(urlStr);
                        string fileExt = Path.GetExtension(urlStr).ToLower();
                        string fileNameWithoutExtension = Path.GetFileNameWithoutExtension(urlStr);
                        var strName = fileNameWithoutExtension.Substring(fileNameWithoutExtension.LastIndexOf("/") + 1) + random.Next(1000, 9999) + fileExt;
                        zipStream.PutNextEntry(new ZipEntry(strName));
                        HttpWebRequest request = (HttpWebRequest)WebRequest.Create(urlStr);
                        request.AllowAutoRedirect = true;
                        WebProxy proxy = new WebProxy();
                        proxy.BypassProxyOnLocal = true;
                        proxy.UseDefaultCredentials = true;
                        request.Proxy = proxy;
                        WebResponse response = request.GetResponse();
                        using (Stream streams = response.GetResponseStream())
                        {
                            Byte[] buffer = new Byte[1024];
                            int current = 0;
                            while ((current = streams.Read(buffer, 0, buffer.Length)) != 0)
                            {
                                zipStream.Write(buffer, 0, current);
                            }
                            zipStream.Flush();
                        }
                    }
                }
                zipStream.Finish();
                zipMs.Position = 0;
                //下边为打包压缩
                MemoryStream stream = zipMs;
                byte[] srcBuf = new Byte[stream.Length];
                stream.Read(srcBuf, 0, srcBuf.Length);
                stream.Seek(0, SeekOrigin.Begin);
                string filePath = Environment.GetFolderPath(Environment.SpecialFolder.Desktop);
                if (!Directory.Exists(filePath))
                {
                    Directory.CreateDirectory(filePath);
                }
                string date = DateTime.Now.ToString("yyyyMMddHHmmss");
                var file_name = "全电发票" + date + ".zip";
                using (FileStream fs = new FileStream(filePath + "\\" + file_name, FileMode.Create, FileAccess.Write))
                {
                    fs.Write(srcBuf, 0, srcBuf.Length);
                    fs.Close();
                    return "下载成功";
                }
            }
            catch (Exception ex)
            {
                return ex.ToString();
            }
        }