将控件属性绑定到Window ViewModel的类的属性

我想将TextBox的Text属性绑定到ViewModel的属性的子级。

这是我的代码：

---

foo.cs:

    public class foo()
    {
      public foo()
      {
        Bar = "Hello World";
      }
      public string Bar { Get; private Set;}
      //Some functions
    }

ViewModel.cs:

    public class ViewModel : INotifyPropertyChanged
    {
      public foo Property { Get; Set; }
      //some more properties
      public ViewModel()
      {
      }
      public event PropertyChangedEventHandler PropertyChanged;        
      protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
      {
          PropertyChangedEventHandler handler = PropertyChanged;
          if (handler != null) handler(this, new PropertyChangedEventArgs(propertyName));            
      }
    }

Window.xaml.cs:

    public ViewModel MyViewModel { get; set; }
    public Window()
    {
      MyViewModel = new ViewModel();
      this.DataContext = MyViewModel;
      MyViewModel.Property = new foo();
    }

Window.xaml:

    <!--
    Some controls
    -->
    <TextBox Text="{Binding Path=Property.Bar}"></TextBox>

我也试过这和这个，但没有一个对我有效。

public class ViewModel : INotifyPropertyChanged
{
  private foo _property;
  public foo Property
  { 
     get{ return _property; }
     set{ _property = value; OnPropertyChanged(); }
  }
  .................