Can WebClient.DownloadDataAsync be encapsulated in one class?

I'm trying to encapsulate the WebClient async download method so I can get an progress bar update while waiting for lengthy files to download. MSDN documentation indicates that FTPDownloadCompleted and FTPDownloadProgressChanged are on a different thread but they never fire. Maybe I'm going about this the wrong way, but I need to avoid synching up events, callbacks ect.. so I thought I'd try this route. I'm particularly curious as to why the events aren't firing if they're delegates on a different thread.

class downloadFTP
{ 
    public delegate void ProgressBarUpdate(Int32 val);
    ProgressBarUpdate progressBarUpdate;

    WebClient webClient;

    Int32 waitTime = 60;

    Double percentComplete = 0;

    Boolean transferComplete = false;
    public Boolean TransferComplete { get { return transferComplete; } }

    Byte[] downloadData = null;

    public Boolean DownLoadFTPFile(String filename, ProgressBarUpdate pbUpdate) 
    {
        Boolean result = false;

        progressBarUpdate = pbUpdate;
        AutoResetEvent waiter = new System.Threading.AutoResetEvent (false);
        webClient = new WebClient();
        webClient.Credentials = new NetworkCredential(user.userId, user.passWd);
        webClient.DownloadDataCompleted += new DownloadDataCompletedEventHandler(FTPDownloadCompleted);
        webClient.DownloadProgressChanged += new DownloadProgressChangedEventHandler(FTPDownloadProgressChanged);
        webClient.DownloadDataAsync(new Uri(ftpURL + "//" + filename),waiter);

        waiter.WaitOne(waitTime*1000);
        return TransferComplete;
    }

    private void FTPDownloadProgressChanged(object sender, DownloadProgressChangedEventArgs e)
    {
        percentComplete = e.ProgressPercentage;
    }

    private void FTPDownloadCompleted(object sender, DownloadDataCompl开发者_如何学PythonetedEventArgs e)
    {
        downloadData = e.Result;
        transferComplete = true;
    }

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WebClient runs callbacks on the current SynchronizationContext (see AsyncOperationManager.CreateOperation).

If the current SynchronizationContext is a WinForms or WPF event loop, then your DownLoadFTPFile method blocks the thread and events won't show up. Solution: Remove the AutoResetEvent.