private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
        {
            richTextBox1.Invoke(new Action(delegate () { richTextBox1.Text += "Downloading file: "; }));

            Task task = new Task (() => {
                WebClient client = new WebClient();
                Console.WriteLine("Down");
                client.DownloadProgressChanged += new DownloadProgressChangedEventHandler(client_DownloadProgressChanged);
                client.DownloadFileCompleted += new AsyncCompletedEventHandler(client_DownloadFileCompleted);
                client.DownloadFileAsync(new Uri("http://distro.ibiblio.org/damnsmall/current/dsl-4.4.10-syslinux.iso"), @"E:\dls.iso");
                while(client.IsBusy);
           });

          task.RunSynchronously();
          richTextBox1.Invoke(new Action(delegate () { richTextBox1.Text += "DONE "+Environment.NewLine; }));