Question

Possible Duplicate:
WPF and cross thread operations

I am having trouble with a window in my wpf application displaying, but not updating the view. When placing the cursor over the opened window the loading icon is shown and the window is unresponsive. I am thinking this is likely due to some threading issue I don’t have enough experience in seeing.

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Here is the setup:

My main program runs on startup and creates and instance of a MainWindow window which implements a custom interface (IPlayer). The main program then runs a process which interracts with IPlayer to accomplish some task, the idea being that the main program requests actions from the MainWindow, which prompts the user for some sort of input and displays the results.

I’ll simplify the code for clarity. Assume this program simply runs a sort of chatter bot game.

class MainProgram
{

    [STAThread]
    static void main(string[] args)
    {
        MainWindow wdw = new MainWindw();
        Game g = new Game(wdw);

        wdw.Show();
        g.RunGame();
    }

}

class Game
{
    public IPlayer p;
    Game(IPlayer) { this.p = p; }

    public RunGame()
    {
        string r = GetResponse("How was your day?");

        ...
    }
}


public partial class Human_Player : Window, IPlayer
{
    public string GetResponse(string Question)
    {
        ShowQuestion(Question);
        string r = GetResponse();
        DisplayResponse(r);
        return r;
    }

    ...
}

I gave running RunGame() in a separate thread a shot like this:

Thread thread = new Thread(new ThreadStart(game.RunGame));
thread.Start(); 

but got an InvalidOperationException in response stating “The calling thread cannot access this object because a different thread owns it.”

Any help here would be appreciated since I’m pretty new to this stuff. Thanks ahead of time!

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EDIT:

Just to clarify, I’m not creating any new threads at the moment. Thus I don’t think I’m doing any multi-threading. I’m attempting to run game.RunGame() on the main thread after opening the window. The runGame method consists of a large loop which calls a method on the Human_Player window that changes the UI.

As far as I know there are only two threads:
– Main Thread – MainProgram and Game run here. I think the windows runs here as well but I could be wrong… please clarify
– Rendering Thread – the UI is rendered here.

Answer 1

Argh, this question is asked soooo many times… You cannot update a GUI control from a different thread than the Dispatcher thread associated to the control. You will need to run your update code using Dispatcher.BeginInvoke to update the GUI from the correct thread.

If you are not running the code from a different thread then it’s possible that your method is taking too long to execute, thus causing the GUI to hang because the event thread is blocked from accepting user input.