Question

The following code doesn’t work, somehow I can’t get the int value from the ‘Completed’ method to my btn_Start_Click method:

private void btn_Start_Click(object sender, EventArgs e)
{
    int completedDownload = 0;      

    WebClient webClient = new WebClient();
    webClient.DownloadFileCompleted += new AsyncCompletedEventHandler(Completed);
    webClient.DownloadFileAsync(new Uri("http://somesite.com/file.jpg"), @"c:\file.jpg");

    if (Completed.completeDownload == 1)
    {
        //open the file code goes here.
    }

    //Rest of the code goes here.
    //and here
    //and here
}

private void Completed(object sender, AsyncCompletedEventArgs e)
{
    completedDownload = 1;
}

Answer 1

From the remarks on the WebClient.DownloadFileAsync function:

The file is downloaded asynchronously using thread resources that are
automatically allocated from the thread pool. To receive notification
when the file is available, add an event handler to the
DownloadFileCompleted event.

MSDN Documentation

It seems like a better choice to fire a function when the file is completed would involve using an event handler. Here is an example using the DownloadFileCompleted handler:

// Sample call : DownLoadFileInBackground2 ("http://www.contoso.com/logs/January.txt");
public static void DownLoadFileInBackground2 (string address)
{
    WebClient client = new WebClient ();
    Uri uri = new Uri(address);

    // Specify that the DownloadFileCallback method gets called
    // when the download completes.
    client.DownloadFileCompleted += new AsyncCompletedEventHandler (DownloadFileCallback2);
    // Specify a progress notification handler.
    client.DownloadProgressChanged += new DownloadProgressChangedEventHandler(DownloadProgressCallback);
    client.DownloadFileAsync (uri, "serverdata.txt");
}

MSDN Documentation