Не могу сделать привязку

Случайный (MyViewModel) -> VMTestValue (MyViewModel) -> TestUserControl (MainWindow) "

MyViewModel» такое ViewModel для "MainWindow»

Весь проект:http://rusfolder.com/32608140

TestUserControl.xaml

TestUserControl.cs

...
public TestUserControl()
        {
            InitializeComponent();

            this.DataContext = this;
        }

        public static readonly DependencyProperty TestValueProperty =
           DependencyProperty.Register("TestValue", typeof(int), typeof(TestUserControl),
               new FrameworkPropertyMetadata((int)255)
               );

        public int TestValue
        {
            set { SetValue(TestValueProperty, value); }
            get
            {
                return (int)GetValue(TestValueProperty);
            }
        }
...

MyViewModel.cs

using System;

using System.Timers;
using Microsoft.Practices.Prism.ViewModel;

namespace TestBinding
{
    class MyViewModel : NotificationObject
    {
        private int _VMTestValue;

        private Timer timer;
        private Random _random;

        public MyViewModel()
        {
            _random=new Random();

            timer=new Timer();
            timer.Interval = 500;
            timer.Elapsed += new ElapsedEventHandler(timer_Elapsed);
            timer.Start();
        }

        void timer_Elapsed(object sender, ElapsedEventArgs e)
        {
            VMTestValue = _random.Next(10, 300);
        }

        public int VMTestValue
        {
            set 
            { 
                _VMTestValue = value;
                this.RaisePropertyChanged(() => this.VMTestValue);
            }
            get { return _VMTestValue; }
        }
    }
}

MainWindow.cs

...
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
            this.DataContext = new MyViewModel();
        }
    }
...

MainWindow.xaml

...


...

Почему я не могу зайти в UserControl?