title: Silverlight - Data binding not listening for PropertyChanged event
body: <p>Could somebody please explain to me what happens here?<br>
  I am creating a binding in code.  </p>
  
  <p>The target object is a UserControl<br>
  The target property is a boolean DependencyProperty<br>
  The source object is a FrameworkElement and implements INotifyPropertyChanged<br>
  The source property is of type ObservableCollection  </p>
  
  <p>What happens:</p>
  
  <ul>
  <li><p>The binding is created in code, the result BindingExpressionBase looks fine, the mode is OneWay, the target value gets set correctly (at this time)</p>
  
  <p>Binding b = new Binding();<br>
  b.Path = "SourceProperty";<br>
  b.Source = SourceObject;<br>
  BindingExpressionBase e = this.SetBinding(TargetProperty, b);  </p></li>
  <li><p>The source property then gets changed as a result of another databinding. The UserControl tries to fire the PropertyChanged event.</p></li>
  <li><p>....but nobody is listening. PropertyChanged is null.</p></li>
  </ul>
  
  <p>I am sure that nothing else is assigned to the target property, so it should still be bound. Why is the binding not listening for the PropertyChanged event?</p>