Question

I’m writing an app in c# for wp7: 2 pages [mainpage, secondpage].
The application starts in mainpage, then the user can navigate to secondpage (using NavigationService.Navigate) in secondpage.

In secondpage WebClient downloads a file in the isolatedStorage.

My problem is that the download freezes when the user returns back to mainpage using the back key!

There is a way to do that in background so the user can navigate throw the pages freely?

Here is the code of the secondpage class (there is also a button with webClient.OpenReadAsync(uri) in the click event).

public partial class SecondPage : PhoneApplicationPage
{
    WebClient webClient = new WebClient();
    IsolatedStorageFile Storage = IsolatedStorageFile.GetUserStoreForApplication();

    public SecondPage()
    {
        InitializeComponent();
        webClient.DownloadProgressChanged += new DownloadProgressChangedEventHandler(webClient_DownloadProgressChanged);
        webClient.OpenReadCompleted += new OpenReadCompletedEventHandler(webClient_OpenReadCompleted);
    }
    void webClient_OpenReadCompleted(object sender, OpenReadCompletedEventArgs e)
    {
        try
        {
            if (e.Result != null)
            {
                string fileName = "download.txt";
                IsolatedStorageFileStream f = new IsolatedStorageFileStream(fileName, System.IO.FileMode.Create, Storage);
                long fileNameLength = (long)e.Result.Length;
                byte[] byteImage = new byte[fileNameLength];
                e.Result.Read(byteImage, 0, byteImage.Length);
                f.Write(byteImage, 0, byteImage.Length);
            }
        }
        catch (Exception ex)
        {
            MessageBox.Show(ex.Message);
        }
    }

    void webClient_DownloadProgressChanged(object sender, DownloadProgressChangedEventArgs e)
    {
        try
        {
            if (ProgressDownload.Value <= ProgressDownload.Maximum)
            {
                ProgressDownload.Value = (double)e.ProgressPercentage;
            }

        }
        catch (Exception ex)
        {
            MessageBox.Show(ex.Message);
        }
    }
}

Thanks

with the BackgroundWorker class i have this issue: when i call the webClient.OpenReadAsync the bw_doWork function (code is under) ends, because that call is async! so the bw reports the completeEvent.

    private void bw_DoWork(object sender, DoWorkEventArgs e)
    {
        BackgroundWorker worker = sender as BackgroundWorker;

        WebClient webClient = new WebClient();
        webClient.DownloadProgressChanged += new DownloadProgressChangedEventHandler(webClient_DownloadProgressChanged);
        webClient.OpenReadCompleted += new OpenReadCompletedEventHandler(webClient_OpenReadCompleted);


        webClient.OpenReadAsync(new Uri("http://foo.com/asd.txt"));

    }

Answer 1

Check out the Background Transfer APIs – sounds like this is exactly what you need to accomplish your requirements.