private void ObserveInternal(INotifyPropertyChanged source, Action whenChanged)
{
this.whenChanged = whenChanged;
if (source != null)
{
// Observes this one.
this.weakHandler = source.AddWeakEventHandler(this.OnPropertyChanged);
// Observes the children.
foreach (var node in this.Nodes.Where(x => x.IsObservable))
{
node.ObserveInternal(node.GetNotiyfPropertyChangedProperty(source), whenChanged);
}
}
}
