DataTemplatingIntro NullReferenceException about wpf-samples HOT 1 OPEN

    public override DataTemplate SelectTemplate(object item, DependencyObject container)
    {
        if (item != null && item is Task)
        {
            var taskitem = (Task)item;
            var window = Application.Current.MainWindow;
            if (taskitem.Priority == 1)
                return ((FrameworkElement)container).FindResource
                    ("ImportantTaskTemplate") as DataTemplate;
      
            return
            ((FrameworkElement)container).FindResource
                    ("MyTaskTemplate") as DataTemplate;
        }
        return null;
    }
}