Example of how to work with MVVM pattern using the MVVMCoffee nuget package - http://julianocustodio.com/mvvmcoffee

App.xaml.cs

using Xamarin.Forms;

namespace Sample
{
    public partial class App : Application
    {
        public App()
        {
            InitializeComponent();

            MainPage = new NavigationPage(new MainPage());
        }
    }
}