从列表中删除不会呼叫设置器？

Question

In my c# app (MVVM Pattern) I have something like this:

 private List<MyClass> _classes= new List<MyClass>();
 public List<MyClass> Classes
    {
        get { return _classes; }
        set
        {
            _servers = value;
            NotifyOfPropertyChange(() => Classes);
            NotifyOfPropertyChange(() => Classes2);
        }
    }
  public List<MyClass> Classes2
    {
        get
        {
           return Classes.Where(class=> class.boolValue).ToList();
        }
    }

And when I use Classes.Add(class) or Classes.Remove(class) setter doesn't called. Why?

Answer 1

Because you aren't changing the Classes property -- you are changing the internal state of the object referenced by Classes . If you need to be notified of changes to the list, you may want to look into ObservableCollection :

http://msdn.microsoft.com/en-us/library/ms668604.aspx

Answer 2

It is because Classes.Add is not setting the Classes property, it is just calling Get then performing the method on the object that was returned. You could force your setter to occur by doing the Add() then re-setting the property ( Classes = Classes ) but that's a bit of a cheat. Your best bet would be to use an ObservableCollection as graham says, or derive your own list class that overrides the Add method to raise an event.