title: When does WPF subscribe to the PropertyChanged event?
body: <p>I have a <code>ClassA</code> with an <code>ObservableCollection</code> property, that implements the <code>INotifyPropertyChanged</code> interface</p>
  
  <p>on my window codebehind I have declared a <code>ClassA variable</code>, and initialize it in the Main() method.</p>
  
  <p>i'd expect that <code>variable.PropertyChanged</code> would have a WPF event wired to it, but apparently the <code>PropertyChanged</code> event remains null</p>