Nie mogę odpalić prostego programu

Cześć
Uczę się C# i Xamarina i mam problem z odpaleniem aplikacji. Ma ona za zadanie po naciśnięciu przycisku pokazać napis albo go ukryć. Chce użyć MVVM i tu właśnie zaczął się problem. Proszę o napisanie mi co powinienem poprawić i gdzie leży błąd

Model

 using System;
namespace TestApp
{
	public class MessageModel
	{
		
		public string Message { get; set; }

	}
}

ViewModel

 using System;
using System.ComponentModel;
using System.Runtime.CompilerServices;


namespace TestApp.ViewModels
{
    public class BaseNotifyPropertyChanged : INotifyPropertyChanged
    {
        #region Fields
        public event PropertyChangedEventHandler PropertyChanged;
        #endregion

        #region Methods
        /// <summary>
        /// OnPropertyChanged
        /// </summary>
        /// <param name="propertyName">thanks to [CallerMemberName] we can call only OnPropertyChanged from object which we want te reget</param>
        protected void OnPropertyChanged([CallerMemberName]string propertyName = "")
        {
            PropertyChangedEventHandler handler = PropertyChanged;
            if (null != handler)
            {
                handler(this, new PropertyChangedEventArgs(propertyName));
            }
        }

        #endregion
    }
}

 using System.Linq;
using System.Threading.Tasks;
using Xamarin.Forms;

namespace TestApp.ViewModels
{
    /// <summary>
    /// BaseViewModel
    /// </summary>
    public abstract class BaseViewModel : BaseNotifyPropertyChanged
    {
        #region Events
        public delegate void NavigateFromDetailPageHandler(ContentPage page);
        public event NavigateFromDetailPageHandler NavigateFromDetailPageEvent;
        private void OnNavigateFromDetailPage(ContentPage page)
        {
            if (NavigateFromDetailPageEvent != null) NavigateFromDetailPageEvent(page);
        }

        public delegate void ResetDetailPageHandler();
        public event ResetDetailPageHandler ResetDetailPageEvent;
        private void OnResetDetailPage()
        {
            if (ResetDetailPageEvent != null) ResetDetailPageEvent();
        }
        #endregion

        #region Fields
        private INavigation _navigation;
        #endregion


        #region Methods
        protected virtual void OnNavigatedFrom() { }

        /// <summary>
        /// BaseViewModel
        /// </summary>
        /// <param name="navigation"></param>
        /// <param name="currentPage"></param>
        public BaseViewModel(INavigation navigation)
        {
            _navigation = navigation;
        }

        public async Task GoBack()
        {
            if (_navigation.NavigationStack.Count > 0)
            {
                await _navigation.PopAsync();
            }
        }

        public abstract void RemoveHandlers();

        #endregion
    }
}

 using System;
using System.Windows.Input;
using TestApp.Commons;
using Xamarin.Forms;

namespace TestApp.ViewModels
{


	public sealed class MessageViewModel : BaseViewModel
	{

		public ICommand ClickCommand { get; set; }
	

		public MessageModel MessageModel { get; set; }

		private bool _isSelect;
		public bool IsSelect
		{
			get
			{
				return _isSelect;
			}
			set
			{
				_isSelect = value;
				OnPropertyChanged();
			}
		}

		private void InitializeCommands()
		{
			ClickCommand = new DelegateCommand(ClickCommandExecute);
		}

		void ClickCommandExecute()
		{
			
			if (IsSelect == true)
					{
						IsSelect = false;
					}
					else IsSelect = true;
		}

		public MessageViewModel(INavigation navigation) : base(navigation)
		{
			
			InitializeCommands();
		}

		internal void InitializeHandlers()
		{
			IsSelect = true;
			MessageModel = new MessageModel
			{
				Message = "Hello World",
			};
		}

		public override void RemoveHandlers()
		{
			throw new NotImplementedException();
		}

	
	}
}

View

 using TestApp.ViewModels;
using Xamarin.Forms;

namespace TestApp.Views
{
    public class ExtendedContentPage : ContentPage
    {
      

        protected override void OnDisappearing()
        {
            if (BindingContext != null)
            {
                (BindingContext as BaseViewModel).RemoveHandlers();
            }

            base.OnDisappearing();
        }
    }
}

 using System;
using TestApp.ViewModels;


namespace TestApp.Views
{
	public partial class MainPageView : ExtendedContentPage
	{

		public MainPageView()
		{
			InitializeComponent();
			BindingContext = new MessageViewModel(Navigation);
		}

	
}
}

 <?xml version="1.0" encoding="UTF-8"?>
<d:ExtendedContentPage xmlns:d="clr-namespace:TestApp.Views;assembly=TestApp"
    xmlns="http://xamarin.com/schemas/2014/forms" xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml" 
	x:Class="TestApp.MainPageView" 
	BackgroundColor="Blue" >
	<Contend.Page>
	<StackLayout VerticalOptions="Center" >
		
	<Label Text="{Binding MessageModel.Message}" HorizontalOptions="Center" IsVisible="{Binding IsSelect}" />
	<Button Text="Click Me" Command="{Binding ClickCommand}" />

	</StackLayout>
	</Contend.Page>	
</d:ExtendedContentPage>

Ok poradziłem sobie już z tym :)