public TestViewModel(Func <TestViewModel, ViewModelBehaviorsController <TestViewModel> > a) : base(a)
        {
            ShowTextCommand = Text.Select(str => !string.IsNullOrWhiteSpace(str)).ToReactiveCommand();

            // determistic start of behaviors
            BehaviorsController.Start();
        }
        public MainPageViewModel(Func <MainPageViewModel, ViewModelBehaviorsController <MainPageViewModel> > controllerFactory) : base(controllerFactory)
        {
            ShowTextCommand = Text.Select(str => !string.IsNullOrWhiteSpace(str)).ToReactiveCommand();

            // determistic start of behaviors
            BehaviorsController.Start();
        }