PocketBook/Sources/BookApp/MainPage.xaml.cs

using BookApp.Pages;
using System.Collections.ObjectModel;
using BookApp.ViewModel;
using System.Diagnostics;

namespace BookApp
{
    public partial class MainPage : ContentPage
    {
        public ViewModelNavigation Nav { get; } = new ViewModelNavigation();

        void OnSelectionChanged(object sender, SelectionChangedEventArgs e)
        {
            Debug.WriteLine(
                $"Selection Changed: Added:{e.CurrentSelection.FirstOrDefault()}, Removed:{e.PreviousSelection.FirstOrDefault()}"
            );
        }

        public MainPage(ViewModelMenu data)
        {
            InitializeComponent();
            BindingContext = data;
        }
    }
}