如何在WPF / C＃中检索Dispatcher.BeginInvoke的值

Question

It's my first question on this forum. I'm a french student, so sorry for my English. In my code i want to extract a value from a Dispatcher.BeginInvoke. Here is the part of my code that is problematic.

public partial class Jouer : Window
{
    // private Timer timer_creer_obstacle;
    private Timer timer_personnage_chute;
    private Timer timer_obstacles_avance;
    private Personnage perso;
    private Decor decor;
    public Jouer()
    {
        InitializeComponent();
        perso = new Personnage("canard-de-bain.png", World);
        decor = new Decor(World);
        // Timer qui gère l'avancé des obstacles
        timer_obstacles_avance = new Timer();
        timer_obstacles_avance.Enabled = true;
        timer_obstacles_avance.Interval = 60;
        timer_obstacles_avance.Elapsed += timer_obstacles_avance_event;
        timer_obstacles_avance.AutoReset = true;
        // Timer qui gère la chute du personnage
        timer_personnage_chute = new Timer();
        timer_personnage_chute.Enabled = true;
        timer_personnage_chute.Interval = 60;
        timer_personnage_chute.Elapsed += timer_personnage_chute_event;
        timer_personnage_chute.AutoReset = true;
    }
    public void timer_personnage_chute_event(object sender, ElapsedEventArgs e)
    {
        perso.Dispatcher.BeginInvoke( // Dispatcher pour utiliser le multithearding
            DispatcherPriority.Normal,
            new Action(() =>
            {
                perso.Chuter();
                perso.WorlFarmeCollision();
            }));

And here is the code of WorldFarmeCollision that return me a bool.

public bool WorlFarmeCollision()
{
    if (this.Y >= 350 || this.Y <= 0)
    {
        App.Current.Shutdown();
        return true;
    }
    else
        return false;
}

I want perso.WordFarmeCollision return a value usable in my Jouer class.

Thanks for your answers.

Answer 1

BeginInvoke is executed asynchronously, thus you can't get the return value instantly.

Change it into Invoke instead.

public void timer_personnage_chute_event(object sender, ElapsedEventArgs e)
{
    bool result = perso.Dispatcher.Invoke( // Dispatcher pour utiliser le multithearding
        () =>
        {
            perso.Chuter();
            return perso.WorlFarmeCollision();
        }
        , DispatcherPriority.Normal);

reference : https://msdn.microsoft.com/en-us/library/hh199426(v=vs.110).aspx

Answer 2

I'm doing this by heart since i don't have a WPF environment set up at the moment. This should point you in the right direction though...

public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();

    }


    private void button_Click(object sender, RoutedEventArgs e)
    {
        Perso perso = new Perso();

        Func<bool> getWorlFarmeCollisionAsyncDelegate = perso.WorlFarmeCollision;

        getWorlFarmeCollisionAsyncDelegate.BeginInvoke(
              (resultASync) =>
              {
                  var methodDelegate = (Func<bool>)resultASync.AsyncState;
                  perso.Dispatcher.BeginInvoke(
                  new Action(() => perso.BoolProperty = methodDelegate.EndInvoke(resultASync)));

              },
              getWorlFarmeCollisionAsyncDelegate);
    }
}

public class Perso
{
    public Dispatcher Dispatcher => Application.Current.Dispatcher;

    public bool BoolProperty { get; set; }

    public bool WorlFarmeCollision()
    {
        return true;
    }

}