ChangeAppStyle only works once

I try to implement a Light/Dark-Switch. When i press the button, ChangeAppStyle works once. When i press it again, nothing happens. No error, no change (only the background). It doesn’t matter, which Theme i choose … if i use BaseDark in App.xaml, i can change once to BaseLight, but not back to BaseDark.

 private void lightDARK_Click(object sender, RoutedEventArgs e)
        {
            try
            {
                MainWindow mw = (MainWindow)Application.Current.MainWindow;
                SolidColorBrush color;
                if (mw.Background.ToString() == "#FF696969")
                {
                    ThemeManager.ChangeAppStyle(this, ThemeManager.GetAccent("Blue"), ThemeManager.GetAppTheme("BaseLight"));
                    color = Brushes.LightGray;
                }
                else
                {
                    ThemeManager.ChangeAppStyle(this, ThemeManager.GetAccent("Blue"), ThemeManager.GetAppTheme("BaseDark"));
                    color = Brushes.DimGray;
                }
                mw.Background = color;
            }

            catch (Exception ex)
            {
                throw new Exception("Error: " + ex.Message);
            }
        }

[DerKiLLa]

Thanks very much! Application.Current works perfectly! 😃

[punker76]