private void OnBlackClick(object sender, RoutedEventArgs e)
{
Dispatcher.BeginInvoke(DispatcherPriority.ApplicationIdle, (ThreadStart)(() =>
{
Application.Current.Resources.BeginInit();
Application.Current.Resources.MergedDictionaries.RemoveAt(1);
Application.Current.Resources.MergedDictionaries.Add(new ResourceDictionary { Source = new Uri("pack://application:,,,/Fluent;component/Themes/Office2010/Black.xaml") });
Application.Current.Resources.EndInit();
}));
}