Manage and cache UI objects

Question

I am writing a namespace extension for windows explorer. In the context of the extension there is no UI thread. So when I create a UI object and cache it to reuse it, I get cross threading exception. I understand why I am getting a cross threading exception but I am not sure how to get around it.

Is there a way I can create my own UI thread and then use that thread to manage the UI objects? I think that'll resolve the issue.

Answer 1

I was able to fix this by writing my own message loop and running the UI from there. In following example, action is the function I call to invoke the UI.

internal class MessageLoop
{
    private bool _running;
    private readonly ConcurrentQueue<Action> _actions = new ConcurrentQueue<Action>();

    [DllImport("user32.dll")]
    static extern int GetMessage(out MSG lpMsg, IntPtr hWnd, uint wMsgFilterMin, uint wMsgFilterMax);
    [DllImport("user32.dll")]
    static extern bool TranslateMessage([In] ref MSG lpMsg);
    [DllImport("user32.dll")]
    static extern IntPtr DispatchMessage([In] ref MSG lpmsg);

    public MessageLoop()
    {
        Start();
    }

    public void Start()
    {
        _running = true;
        Thread t = new Thread(RunMessageLoop) {Name = "UI Thread", IsBackground = true};
        t.SetApartmentState(ApartmentState.STA);
        t.Start();
    }

    private void RunMessageLoop()
    {
        while (_running)
        {
            while (_actions.Count > 0)
            {
                Action action;

                if (_actions.TryDequeue(out action))
                    action();
            }

            MSG msg;
            var res = GetMessage(out msg, IntPtr.Zero, 0, 0);

            if (res <= 0)
            {
                _running = false;
                break;
            }

            TranslateMessage(ref msg);
            DispatchMessage(ref msg);
        }
    }

    public void Stop()
    {
        _running = false;
    }

    public void AddMessage(Action act)
    {
        _actions.Enqueue(act);
    }
}