CODEWITHSUNDEEP
c#wpfmultithreading
Sampath
Sampath

Reputation: 1211

Why do I sometimes get an "Invalid window handle" exception when creating a window in a different thread

I'm getting an "Invalid window handle" exception when creating a Window as per below code. This is invoked on a seperate thread. It is not thrown every time but occurs randomly. Also I cannot view the stack trace for the exception and it says "{Unable to evaluate expression because the code is optimized or a native frame is on top of the call stack.}"

private void ShowDialog()
{
    Thread thread = new Thread(() =>
        {
            waitContainer = MakeSimpleWindow();
            this.waitContainer.Closed += new EventHandler(waitingWindow_Closed);

            waitContainer.ShowDialog();

            System.Windows.Threading.Dispatcher.Run();
        });
        thread.SetApartmentState(ApartmentState.STA);
        thread.IsBackground = true;
        thread.Start();
}

public Window MakeSimpleWindow()
    {
        Window w = new Window(); // Exception occurs from here
        w.Title = Attributes[MessageBoxAttribute.message];            
        return w;
    }

Upvotes: 2

Views: 4451

Answers (1)

Henk Holterman
Henk Holterman

Reputation: 273244

The 2 lines:

waitContainer.ShowDialog();\    
System.Windows.Threading.Dispatcher.Run();

at the very least have a race condition. When ShowDialog starts executing, the Thread is not yet running a Dispatcher.

But the answer is not how to fix this. While you can execute more that 1 dispatcher, it is rarely a good idea. Look for a solution where you run 1 GUI thread (the main thread) and resolve the other issues with Invoke and events.

Upvotes: 5

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