Question

I want to create a thread with a Dispatcher and then, from another thread, use that dispatcher to queue work with different priorities. i.e.

var dispatcher = GetNewThreadDispatcher();
dispatcher.BeginInvoke(longRunningTask1, DispatcherPriority.Normal);
dispatcher.BeginInvoke(longRunningTask2, DispatcherPriority.Background);
dispatcher.BeginInvoke(longRunningTask3, DispatcherPriority.Normal);

In this case, the background thread would perform longRunningTask1, then longRunningTask2, longRunningTask3. I’m having difficulty creating a clean GetNewThreadDispatcher(), any help?

Answer 1

You can try to create new background thread ( http://msdn.microsoft.com/en-us/library/7a2f3ay4(v=vs.90).aspx) and get Dispatcher for it:

Dispatcher dispatcher = Dispatcher.FromThread(workerThread);

Some edits:
You need to execute
Dispatcher dispatcher=Dispatcher.CurrentDispatcher or Dispatcher.Run inside OnThreadStart. But interesting thing: after execute

workerThread.Start();
Dispatcher dispatcher = Dispatcher.FromThread(workerThread);  

dispatcher is null but after execute

workerThread.Start();
Console.WriteLine("main thread: Starting worker thread...");
Dispatcher dispatcher = Dispatcher.FromThread(workerThread); 

dispatcher is filling

added:

    static void OnThreadStart()
    {
       Dispatcher.Run();
    }


    private Dispatcher GetNewThreadDispatcher()
    {
        Thread workerThread=null;
        try
        {
           workerThread = new Thread(OnThreadStart);
           workerThread.IsBackground = true;
           workerThread.Start();
           int waitingCiclesCount = 100;
           int cicleIndex = 0;
           int sleepTimeInMiliseconds = 100;
           Dispatcher dispatcher = null;
           while (cicleIndex < waitingCiclesCount)
           {
               dispatcher = Dispatcher.FromThread(workerThread);
               if (dispatcher!=null)
                   break;
               Thread.Sleep(sleepTimeInMiliseconds);
               cicleIndex = cicleIndex + 1;

           }
           if (dispatcher==null)
           {
               workerThread.Abort();
               return null;
           }
           Console.WriteLine(String.Format("thread with id={0} started", workerThread.ManagedThreadId));
           return dispatcher;
        }
        catch (Exception)
        {
            if (workerThread!=null)
                workerThread.Abort();
            return null;
        }
    }

    public MainWindow()
    {
        InitializeComponent();

        TestWorker worker=new TestWorker();
        Dispatcher dispatcher1 = GetNewThreadDispatcher();
        if(dispatcher1!=null)
            dispatcher1.BeginInvoke(new TestDelegate(worker.DoWork1), DispatcherPriority.Normal);
        else
        {
            MessageBox.Show("Cant create dispatcher1");
        }
        Dispatcher dispatcher2 = GetNewThreadDispatcher();
        if (dispatcher2!=null)
            dispatcher2.BeginInvoke(new TestDelegate(worker.DoWork2), DispatcherPriority.Normal);
        else
        {
            MessageBox.Show("Cant create dispatcher2");
        }
    }   

this code working in my test wpf app but i am not expert in multithreading. May be someone will correct me or add some info to this reply.