Question

Downloading Zip files with webclient seems to not be working properly for me, once downloaded and saved the zip file comes up as invalid or corrupted, opening with a zip reader. However the source zip file seems to be fine, its a valid zip.

Download code:

using (WebClient webClient = new WebClient())
        {
            webClient.DownloadFileCompleted += new AsyncCompletedEventHandler(Completed);
            webClient.DownloadProgressChanged += new DownloadProgressChangedEventHandler(ProgressChanged);
            webClient.DownloadFileAsync(new Uri(URL), downloadZipFilename);
        }
private void ProgressChanged(object sender, DownloadProgressChangedEventArgs e)
    {
        progressBar.Value = e.ProgressPercentage;
    }

    private void Completed(object sender, AsyncCompletedEventArgs e)
    {
        //unzip
        using (ZipFile zipFile = ZipFile.Read(currentTemporaryDownloadFileUrl))
        {
            zipFile.ExtractAll(currentTargetFileUrl);
        }
        File.Delete(currentTemporaryDownloadFileUrl);
        DownloadFinished(this,EventArgs.Empty);
        Console.WriteLine("File finished downloading.");
    }

The zip extract comes up as corrupt.

Server code:

 //send file
                    e.Response.Connection.Type = HttpServer.Headers.ConnectionType.Close;
                    byte[] buffer = ReadFile(filePath);
                    e.Response.Body.Write(buffer, 0, buffer.Length);

Readfile on server:

public static byte[] ReadFile(string filePath)
        {
            // this method is limited to 2^32 byte files (4.2 GB)

            FileStream fs = File.OpenRead(filePath);
            try
            {
                byte[] bytes = new byte[fs.Length];
                fs.Read(bytes, 0, Convert.ToInt32(fs.Length));
                fs.Close();
                return bytes;
            }
            finally
            {
                fs.Close();
            }
        }

What’s wrong here?

Thanks,
Christian Stewart

Answer 1

Rather than, inefficiently, loading the ZIP file into memory, then writing it out, how about using

e.Response.TransmitFile(filePath);

TransmitFile streams directly to the output stream without buffering, thus minimising memory consumption.