public ViewModelIncrementAgePage()
        {
            InitializeComponent();

            p = new PersonViewModel()
            {
                FirstName = "Tadafumi",
                LastName = "Iriya",
                Age = 17,
            };

            this.DataContext = p;
        }
        public SimpleViewModelPage()
        {
            InitializeComponent();

            var p = new PersonViewModel()
            {
                FirstName = "Tadafumi",
                LastName = "Iriya",
                Age = 17,
            };

            this.DataContext = p;
        }