C# Thread Queue Synchronize

Question

Greetings, I am trying to play some audio files without holding up the GUI. Below is a sample of the code:

if (audio)
{
    if (ThreadPool.QueueUserWorkItem(new WaitCallback(CoordinateProc), fireResult))
    {

    }
    else
    {
        MessageBox.Show("false");
    }
}

if (audio)
{
    if (ThreadPool.QueueUserWorkItem(new WaitCallback(FireProc), fireResult))
    {

    }
    else
    {
         MessageBox.Show("false");
    }
}

if (audio)
{
    if (ThreadPool.QueueUserWorkItem(new WaitCallback(HitProc), fireResult))
    {

    }
    else
    {
        MessageBox.Show("false");
    }
}

The situation is the samples are not being played in order. some play before the other and I need to fix this so the samples are played one after another in order.

How do I implement this please?

Thank you.

EDIT: ThreadPool.QueueUserWorkItem(new WaitCallback(FireAttackProc), fireResult);

I have placed all my sound clips in FireAttackProc. What this does not do and I want is: wait until the thread stops running before starting a new thread so the samples dont overlap.

Answer 1

Why not just create one "WorkItem" and do everything there?

Answer 2

You should have a look at the BackgroundWorker option !

Answer 3

You can't guarrantee the order of execution of thread pool threads. Rather than that, as suggested by others, use a single thread to run the procs in order. Add the audio procs to a queue, run a single thread that pulls each proc off the queue in order and calls them. Use an event wait handle to signal the thread each time a proc is added to the queue.

An example (this doesn't completely implement the Dispose pattern... but you get the idea):

public class ConcurrentAudio : IDisposable
{
    public ConcurrentAudio()
    {
        _queue = new ConcurrentQueue<WaitCallback>();
        _waitHandle = new AutoResetEvent(false);
        _disposed = false;
        _thread = new Thread(RunAudioProcs);
        _thread.IsBackground = true;
        _thread.Name = "run-audio";
        _thread.Start(null); // pass whatever "state" you need
    }

    public void AddAudio(WaitCallback proc)
    {
        _queue.Enqueue(proc);
        _waitHandle.Set();
    }

    public void Dispose()
    {
        _disposed = true;
        _thread.Join(1000); // don't feel like waiting forever
        GC.SuppressFinalize(this);
    }

    private void RunAudioProcs(object state)
    {
        while (!_disposed)
        {
            try
            {
                WaitCallback proc = null;

                if (_queue.TryDequeue(out proc))
                    proc(state);
                else
                    _waitHandle.WaitOne();
            }
            catch (Exception x)
            {
                // Do something about the error...
                Trace.WriteLine(string.Format("Error: {0}", x.Message), "error");
            }
        }
    }

    private ConcurrentQueue<WaitCallback> _queue;
    private EventWaitHandle _waitHandle;
    private bool _disposed;
    private Thread _thread;
}