Xamarin.Forms BasePage

BasePage.cs

namespace ... {
	// for supporting this
	// public partial class "Derived"Page : "Derived"PageXaml {.... } for a xaml/cs page
	// then
	// <?xml version="1.0" encoding="utf-8" ?><local:"Derived"tPageXaml xmlns="ht...
	// with this bit in the cs file
	// public partial class "Derived"PageXaml : BasePageOverrideBackButton<ViewModel."Derived"ViewModel> {	}
	public class BasePageOverrideBackButton<T> : BasePage<T> where T : ViewModel.BaseViewModel, new() { 
		public BasePageOverrideBackButton() : base() {
		}

		protected override bool OnBackButtonPressed() {
			base.OnBackButtonPressed();
			App.GoHome();
			return true;
		}
	}

	#region BasePage with ViewModel
	public class BasePage<T> : BasePage where T : ViewModel.BaseViewModel, new() {
		protected T viewModel;

		public BasePage() : base() {
			BindingContext = ViewModel;
		}

		public T ViewModel {
			get {
				return viewModel ?? (viewModel = new T());
			}
		}

		~BasePage() {
			viewModel = null;
		}
	}
	#endregion	
	
  public class BasePage : ContentPage {
    // idea from XLabs
    protected override void OnAppearing() {
			base.OnAppearing();
			if (BindingContext != null && BindingContext is BaseViewModel) {
				var vm = (BaseViewModel)BindingContext;
				vm?.OnAppearing();
       // more stuff... build toolbar items...dance a jig.
			}
    }
    protecte override void OnDisappearing() {
			base.OnDisappearing();
			if (BindingContext != null && BindingContext is BaseViewModel) {
				var vm = (BaseViewModel)BindingContext;
				vm?.OnDisappearing();
			}
    }
    
    // override Androids back button, for when I'm running an app with MasterDetail and only want certain pages to exit the app.
	protected override bool OnBackButtonPressed() {
		base.OnBackButtonPressed();
		App.GoHome(); // go to a home screen or where ever
		return true;
	}
  }
}