public MainPageViewModel()
        {
            _notif = new PropertyChangedNotifier(this, () => PropertyChanged);
            _svc = new MvvmCollectionServiceClient();
            _people = new ObservableCollection<Person>();

            _svc.ListPeopleCompleted += new EventHandler<ListPeopleCompletedEventArgs>(_svc_ListPeopleCompleted);
        }
        private static void OnPropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            PropertyChangedNotifier notifier = (PropertyChangedNotifier)d;

            if (notifier != null)
            {
                notifier.propertyChangedAction(notifier.PropertySource, e.NewValue);
            }
        }