public App()
        {
            Xamarin.FormsBook.Toolkit.Toolkit.Init();

            // Instantiate AppData and set property.
            AppData = new AppData();

            // Go to the home page.
            MainPage = new NavigationPage(new DataTransfer5HomePage());
        }
        public App()
        {
            // Ensure link to Toolkit library.
            new Xamarin.FormsBook.Toolkit.ObjectToIndexConverter<object>();

            // Instantiate AppData and set property.
            AppData = new AppData();

            // Go to the home page.
            MainPage = new NavigationPage(new DataTransfer5HomePage());
        }