Question

I have a XAML application that serves as the UI for an automation. The entire automation can take anywhere from 20-30 hours to fully execute so I created a Task class object that essentially wraps Thread methods (Start/Stop/Reset).

However, when I run the automation method under the Task object, the XAML UI is busy and I cannot interact with the other controls, including the Pause button which toggles the Thread.Set() flag.

There is another post
Prevent UI from freezing without additional threads

where someone recommended the BackgroundWorker class this MSDN article mentions it is a bad idea to use this when if it manipulates objects in the UI, which mine does for purposes of displaying status counts:
http://msdn.microsoft.com/en-us/library/system.componentmodel.backgroundworker.aspx

Any idea around this?

    private void OnButtonStartAutomationClick(object sender, RoutedEventArgs e)
    {
        btnPauseAutomation.IsEnabled = true;
        Automation.Task AutomationThread = new Automation.Task(RunFullAutomation);
    }

    private void RunFullAutomation()
    {
        // do stuff that can take 20+ hours
        // threaded so I can utilize a pause button (block)
    }

class Task
{
    private ManualResetEvent _shutdownFlag = new ManualResetEvent(false);
    private ManualResetEvent _pauseFlag = new ManualResetEvent(true);
    private Thread _thread;
    private readonly Action _action;

    public Task(Action action)
    {
        _action = action;
    }

    public void Start()
    {
        ThreadStart ts = new ThreadStart(DoDelegatedMethod);
        _thread = new Thread(ts);            
        _thread.Start();
        _thread.Priority = ThreadPriority.Lowest;
    }

    public void Resume()
    {
        _pauseFlag.Set();
    }

    public void Stop()
    {
        _shutdownFlag.Set();
        _pauseFlag.Set();
        _thread.Join();
    }

    private void DoDelegatedMethod()
    {
        do
        {
            _action();
        }
        while (!_shutdownFlag.WaitOne(0));
    }
}

Answer 1

where someone recommended the BackgroundWorker class this MSDN article mentions it is a bad idea to use this when if it manipulates objects in the UI, which mine does for purposes of displaying status counts

BackgroundWorker is actually ideal for this, as it was designed for this type of scenario. The warning is that you shouldn’t change UI elements inside of DoWork, but rather via ReportProgress and the ProgressChanged event.

The reason the warning exists is “DoWork” is executed on a background thread. If you set a UI element value from there, you’ll get a cross threading exception. However, ReportProgress/ProgressChanged automatically marshals the call back into the proper SynchronizationContext for you.