订阅INotifyPropertyChanged的嵌套（子）对象

更新：问题解决了，请参阅my答。

UPDATE: Problem solved, see my Answer.

我在寻找一个干净和优雅解决方案来处理嵌套的（子）对象的 INotifyPropertyChanged的事件。例如：code：

I'm looking for a clean and elegant solution to handle the INotifyPropertyChanged event of nested (child) objects. Example code:

public class Person : INotifyPropertyChanged {

  private string _firstName;
  private int _age;
  private Person _bestFriend;

  public string FirstName {
    get { return _firstName; }
    set {
      // Short implementation for simplicity reasons
      _firstName = value;
      RaisePropertyChanged("FirstName");
    }
  }

  public int Age {
    get { return _age; }
    set {
      // Short implementation for simplicity reasons
      _age = value;
      RaisePropertyChanged("Age");
    }
  }

  public Person BestFriend {
    get { return _bestFriend; }
    set {
      // - Unsubscribe from _bestFriend's INotifyPropertyChanged Event
      //   if not null

      _bestFriend = value;
      RaisePropertyChanged("BestFriend");

      // - Subscribe to _bestFriend's INotifyPropertyChanged Event if not null
      // - When _bestFriend's INotifyPropertyChanged Event is fired, i'd like
      //   to have the RaisePropertyChanged("BestFriend") method invoked
      // - Also, I guess some kind of *weak* event handler is required
      //   if a Person instance i beeing destroyed
    }
  }

  // **INotifyPropertyChanged implementation**
  // Implementation of RaisePropertyChanged method

}

专注于最好的朋友属性和它的值设置器。现在的我知道我能做到这一点手动，落实在评论中描述的所有步骤。但是，这将是一个很大的code，尤其是当我打算有许多子属性实施 INotifyPropertyChanged的这样的。当然，他们不会是总是相同的类型，他们有共同的唯一的事情就是 INotifyPropertyChanged的接口。

Focus on the BestFriend Property and it's value setter. Now I know that I could do this manually, implementing all steps described in the comments. But this is going to be a lot of code, especially when I'm planning to have many child properties implementing INotifyPropertyChanged like this. Of course they are not going to be always of same Type, the only thing they have in common is the INotifyPropertyChanged interface.

的原因是，在我的现实情况下，我有一个复杂的项目（中车）对象已超过数层嵌套的对象属性（项目是有一个许可证的对象，其本身可以有子再次对象），我需要得到通知的有关项目中的任何一个变化，以便能够重新计算价格。

The reason is, that in my real scenario, I have a complex "Item" (in cart) object which has nested object properties over several layers (Item is having a "License" object, which can itself have child objects again) and I need to get notified about any single change of the "Item" to be able to recalculate the price.

你一些好的建议，甚至一些 实施帮我解决 这个？

Do you some good tips or even some implementation to help me to solve this?

不幸的是，我不能/不允许使用生成后的步骤类似PostSharp实现我的目标。

Unfortunately, I'm not able/allowed to use post-build steps like PostSharp to accomplish my goal.

非常感谢你在前进，
- 托马斯

Thank you very much in advance,
- Thomas