Get notified when properties change in the Model

Question

There seems to be conflicting thoughts on whether INotifyPropertyChanged should be implemented in the Model or not. I think that it should be implemented in the Vie

Answer 1

Save for the typos you pretty much have it ;)

All you would need to add is your constructor and property definitions:

public class PersonViewModel : INotifyPropertyChanged
{
    Person _person;

    public event PropertyChangedEventHandler PropertyChanged;

    protected virtual void OnPropertyChanged(string propertyName)
    {
        var handler = PropertyChanged;
        if (handler != null)
        {
            var e = new PropertyChangedEventArgs(propertyName);
            handler(this, e);
        }
    }

    public PersonViewModel(Person person)
    {
        _person = person;
    }

    public int Age
    {
        get
        {
            return _person.Age;
        }
        set
        {
            _person.Age = value;
            OnPropertyChanged("Age");
        }
    }
}

If you have a choice, I would definitely recommend implementing INotifyPropertyChanged in the Model because you won't havae to worry about translating Models to ViewModels and back.

But if you can't, see above :)