protected override void OnBuyCommandExecute()
 {
     if (Quantity == default(float))
     {
         base.OnBuyCommandExecute();
     }
     else if (IncrementCommand != null && IncrementCommand.CanExecute())
     {
         IncrementCommand.Execute();
     }
 }
        public CanExecuteChangedAsObservableViewModel()
        {
            IncrementCommand = new[] { IsChecked1, IsChecked2 }
            .CombineLatestValuesAreAllTrue()
            .ToReactiveCommand()
            .WithSubscribe(() => Counter.Increment(), CompositeDisposable.Add);

            CanExecuteIncrementCommand = IncrementCommand.CanExecuteChangedAsObservable()
                                         .Select(_ => IncrementCommand.CanExecute())
                                         .ToReadOnlyReactiveProperty()
                                         .AddTo(CompositeDisposable);
        }