Question

I am working on this example, but I am unable to mesh the callback and the threading.
What I want is this.
1) Press button
2) Start the progress bar running
3) Call to a new thread to perform some long running process
4) A callback on the long running process should trigger the progress bar to stop.

Below I have something…Although the callback parameter for DoSomethingInThread comes in as null.
The StopProgressBar() acts on the ProgressBar control, so it cannot be static.

    static bool done;
    static readonly object locker = new object();
    static ParameterizedThreadStart threadStarter = new ParameterizedThreadStart(DoSomethingInThread);  
    private Thread workerThread = new Thread(threadStarter);
    public delegate void StopProgressBarCallback()

    public Form1()
    {
        InitializeComponent();
    }

    private void button1_Click(object sender, EventArgs e)
    {
        StartProgressBar();
        workerThread.Start();
    }

    static void DoSomethingInThread(object callback)
    {
        StopProgressBarCallback stopper = callback as StopProgressBarCallback;
        lock (locker)
        {
            Thread.Sleep(5 * 1000);
        }
        stopper();
    }

    private void StartProgressBar()
    {
        progressBar1.MarqueeAnimationSpeed = 30;
        progressBar1.Style = ProgressBarStyle.Marquee;
    }

    public void StopProgressBar()
    {
        progressBar1.Style = ProgressBarStyle.Continuous;
    }

Answer 1

Have a look at the backgroundworker class, it is more suitable for what you are trying to do and a whole lot easier to get to grips with!

Generally, you shouldn’t ever be ‘newing’ up Thread instances. It is better to use the thread pool, a background worker or if you’re on .net 4, a task object from the thread parallel library.