c# - Launching a WPF Window in a Separate Thread

Question

I'm using the following code for to open a window in a separate thread

public partial class App : Application
{
    protected override void OnStartup(StartupEventArgs e)
    {
        base.OnStartup(e);
    }

    private void button1_Click(object sender, RoutedEventArgs e)
    {
        Thread newWindowThread = new Thread(new ThreadStart(() =>
        {
            // Create and show the Window
            Config tempWindow = new Config();
            tempWindow.Show();
            // Start the Dispatcher Processing
            System.Windows.Threading.Dispatcher.Run();
        }));

        // Set the apartment state
        newWindowThread.SetApartmentState(ApartmentState.STA);
        // Make the thread a background thread
        newWindowThread.IsBackground = true;
        // Start the thread
    }
}

If I use this code in a method, it works. But when I use it as follows, I get an error:

public partial class App : Application
{
    #region Instance Variables
    private Thread newWindowThread;

    #endregion

    protected override void OnStartup(StartupEventArgs e)
    {
        base.OnStartup(e);
        newWindowThread = new Thread(new ThreadStart(() =>
        {
            // Create and show the Window
            Config tempWindow = new Config();
            tempWindow.Show();
            // Start the Dispatcher Processing
            System.Windows.Threading.Dispatcher.Run();
        }));
    }

    private void button1_Click(object sender, RoutedEventArgs e)
    {
        // Set the apartment state
        newWindowThread.SetApartmentState(ApartmentState.STA);
        // Make the thread a background thread
        newWindowThread.IsBackground = true;
        // Start the thread
    }
}

It throws the following error:

System.Threading.ThreadStateException
The state of the thread was not valid to execute the operation

What is the cause of this?

Answer 1

@d.moncada, @JPVenson, @TomTom sorry for everyone, espetially to @d.moncada, your answer made me realize my true error, indeed if run once until my code works. But my really problem is that i try to push button1_Click in two ocation, really i take a timer that called a method with the line of the

 private void button1_Click(object sender, RoutedEventArgs e)

Now the solution of my problem is Detecting a Thread is already running in C# .net?