Question

I’m trying to make a class with a downloader that I can keep reusing so I don’t get a enormous code after a while. But I can’t seem to return the client_DownloadProgressChanged event. This is the code I have right now:

public static string progress;
    public static int percent;
    static WebClient client = new WebClient();
    /// <summary>
    /// Download a file from the internet
    /// </summary>
    /// <param name="url">The URL to download from</param>
    /// <param name="path">The path to save to don't forget the / at the end</param>
    /// <param name="filename">The filename of the file that is going to be download</param>
    public static string DownloadFile(string url, string path, string filename)
    {
        try
        {
            Thread bgThread = new Thread(() =>
                                             {
                                                 client.DownloadProgressChanged += client_DownloadProgressChanged;
                                                 client.DownloadFileCompleted += client_DownloadFileCompleted;
                                                 client.DownloadFileAsync(new Uri(url), path + filename);
                                             });
            bgThread.Start();
        }
        catch (Exception e)
        {
            Console.WriteLine(e.ToString());
        };
        return progress;
    }

    static void client_DownloadProgressChanged(object sender, DownloadProgressChangedEventArgs e)
    {
        double bytesIn = double.Parse(e.BytesReceived.ToString(CultureInfo.InvariantCulture));
        double totalBytes = double.Parse(e.TotalBytesToReceive.ToString(CultureInfo.InvariantCulture));
        double percentage = bytesIn/totalBytes*100;
        progress = "Downloaded " + e.BytesReceived + " of " + e.TotalBytesToReceive;
        percent = int.Parse(Math.Truncate(percentage).ToString(CultureInfo.InvariantCulture));
        while (client.IsBusy)
        {
            return progress;
        }
    }

Answer 1

First of all your Thread is redundant. If you read msdn article about DownloadFileAsync you will see:

This method does not block the calling thread.

Having that in mind you method gets simpler:

public static string DownloadFile(string url, string path, string filename, Action<string,double> progressNotification,Action finishNotification)
{
     DownloadProgressChangedEventHandler progressReaction  = (s,e)=>
              {                               
                      var progress = "Downloaded " + e.BytesReceived + " of " + e.TotalBytesToReceive;
                      var percent = Math.Truncate(e.BytesReceived / (double)e.TotalBytesToReceive * 100);

                      while (client.IsBusy)
                      {
                         progressNotification(progress, percent);
                      }                          
              };
     WebClient client = new WebClient();
     client.DownloadProgressChanged += progressReaction;
     client.DownloadFileCompleted += (s,e) => finishNotification();
     client.DownloadFileAsync(new Uri(url), path + filename);
}                           

I’ve added two method arguments that will be called when progress is made or when download finishes.

To call this method use:

DownloadFile(url,path,fileName,
 (message,precentage)=>{ /* do some progress bar update or something */ },
 ()=>{ /* hide progressbar or some logic after finish */});