The calling thread cannot access this object because a diffe

mohsen hadaeghi

13y2.4k

Hi, I'm Mohsen. I have a bad problem in my code.Please help me for solve my problem.

Button button;
private void Window_Loaded(object sender, RoutedEventArgs e)
{
var threadstart = new Thread(new ThreadStart(Create));
threadstart.SetApartmentState(ApartmentState.STA);
threadstart.Start();
threadstart.Join();

threadstart = new Thread(new ThreadStart(Attach));
threadstart.Start();
threadstart.Join();
}
private void Create()
{
button = new Button();
button.HorizontalAlignment = System.Windows.HorizontalAlignment.Stretch;
button.VerticalAlignment = System.Windows.VerticalAlignment.Stretch;
}
private void Attach()
{
Dispatcher.BeginInvoke(new Action(() =>
{
Canvas.SetTop(button, 0); <===== The calling thread cannot access this object because a different thread owns it.
Canvas.SetLeft(button, 0);
MyCanvas.Children.Add(button);
}));
}

2 Replies

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mohsen hadaeghi13y ago
Thank you for answer my question.
but in my code is run in Windows Form Application and it work.
for example I create one thread for create button and second thread must add button control in my form(with Invoke method). but in Windows Presentation Fundation it has one error. :(
Can you show me a another solution for solve my problem?
Vulpes13y ago
I don't think it's possible to fix it as it stands.

The button is created on the 'Create' thread and that thread will have ended by the time the 'Attach' thread is started.

Dispatcher.BeginInvoke will marshal the code in the Action delegate to the main thread and since the button wasn't created on that thread, it can't be accessed from there.

button1.Dispatcher.BeginInvoke can't be used either because the thread on which button1 was created no longer exists and Canvas controls are also being accessed in the lambda expression.

So, I think you'll have to create the button on the main thread to get this code to work.