Can I create a download progress bar inside an iterator block?

Question

I know progress bars by themselves have been already asked to death, but I'm having trouble with one. I need to download a file via FTP, I'm using WebClient, the downloaded data has to be saved to a byte array, but WebClient.DownloadDataAsync can't return it directly, so I have to use the DownloadDataCompleted method to acces the data. Everything up till there is ok, but the problem is that I can't "pause" the IEnumerator block without blocking the whole thread, and if I don't pause it, the app crashes because the byte array doesn't exist when it tries to access it. When the file to download was in http I used WWW and had no problems, but it had to be moved to FTP. Using WebClient.DownloadData works, but I was asked to include a progress bar. Anyway, here´s the code:

    IEnumerator DownloadGame(Dictionary<string, string> settingsDict)
    {
       statusText = "Starting download...";
       WebClient request = new WebClient();
       request.Credentials = new NetworkCredential("user", "password");
       request.DownloadDataCompleted += DownloadDataCompleted;

      //byte[] fileData = request.DownloadData(settingsDict["downloadlink"]); This works, but is no good since it blocks the thread
    request.DownloadDataAsync(new Uri(settingsDict["downloadlink"]),"somefilepath");


    //do{}while(!downloadFinished); This also works but blocks the thread anyway


    //Process the update
    string tmpRoot = TMPFolder();
    string tmpFolder = tmpRoot + Application.platform + settingsDict["latestVersion"] + "/";
    if (!UnzipUpdate(fileData, tmpFolder))//fail here, in this case fileData is global
    {
        DeleteDirectory(tmpRoot); 
        yield break;
    }
    if (!ProcessUpdateData(tmpFolder))
    {
        DeleteDirectory(tmpRoot); 
        yield break;
    }
    DeleteDirectory(tmpRoot);

    settingsDict["thisVersion"] = GetNextVersion();
}

 void DownloadDataCompleted(object sender, DownloadDataCompletedEventArgs e){

   fileData = e.Result;
   downloadFinished = true;
 }

Answer 1

you can use something like this based on a previous Stakoverflow post..

The easiest is to use BackgroundWorker and put your code into DoWork event handler. And report progress with BackgroundWorker.ReportProgress.

The basic idea:

private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
{
    var ftpWebRequest = (FtpWebRequest)WebRequest.Create("ftp://xxx.com");
    ftpWebRequest.Method = WebRequestMethods.Ftp.UploadFile; //or DownLoad
    using (var inputStream = File.OpenRead(fileName))
    using (var outputStream = ftpWebRequest.GetRequestStream())
    {
        var buffer = new byte[1024 * 1024];
        int totalReadBytesCount = 0;
        int readBytesCount;
        while ((readBytesCount = inputStream.Read(buffer, 0, buffer.Length)) > 0)
        {
            outputStream.Write(buffer, 0, readBytesCount);
            totalReadBytesCount += readBytesCount;
            var progress = totalReadBytesCount * 100.0 / inputStream.Length;
            backgroundWorker1.ReportProgress((int)progress);
        }
    }
}

private void backgroundWorker1_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
    progressBar.Value = e.ProgressPercentage;
}

Make sure WorkerReportsProgress is enabled

backgroundWorker2.WorkerReportsProgress = true;

With BackgroundWorker you can also easily implement upload cancellation.