Question

I need to create two (or more) WPF windows from the same process. But the windows must be handled by separate threads because they should not be able to block each other. How do I do this?

In WinForms this is achieved by:

• Start a new thread
• Create a form from the new thread
• Call Application.Run with the form as parameter

But how do I do the same in WPF?

Answer 1

As msdn states:

private void NewWindowHandler(object sender, RoutedEventArgs e)
{       
    Thread newWindowThread = new Thread(new ThreadStart(ThreadStartingPoint));
    newWindowThread.SetApartmentState(ApartmentState.STA);
    newWindowThread.IsBackground = true;
    newWindowThread.Start();
}

private void ThreadStartingPoint()
{
    Window1 tempWindow = new Window1();
    tempWindow.Show();       
    System.Windows.Threading.Dispatcher.Run();
}

EDIT:
this IS an old answer, but since it seems to be visited often, I could also think of the following modifications/improvements (not tested).

If you would like to close such a window, simply keep a reference to the Window object from outside of the thread (delegate), and then invoke close on it, something like this:

void CloseWindowSafe(Window w)
{
    if (w.Dispatcher.CheckAccess())
        w.Close();
    else
        w.Dispatcher.Invoke(DispatcherPriority.Normal, new ThreadStart(w.Close));
}

// ...
CloseWindowSafe(tempWindow);

If the new thread could become terminated (aborted forcibly), in line with question in comments:

private void ThreadStartingPoint()
{
    try{
        Window1 tempWindow = new Window1();
        tempWindow.Show();       
        System.Windows.Threading.Dispatcher.Run();
    }
    catch(ThreadAbortException)
    {
        tempWindow.Close();
        System.Windows.Threading.Dispatcher.InvokeShutdown();
    }
    //the CLR will "rethrow" thread abort exception automatically
}

DISCLAIMER: don’t do this at home, aborting threads is (almost always) against best practices. Threads should be gracefully handled via any of the various synchronization techniques, or in this case, simply via an invoked window.Close()