MVVM:ViewModel片段

public class ViewModelBase : INotifyPropertyChanged
    {
        public event PropertyChangedEventHandler PropertyChanged;

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

    public class ViewClass : ViewModelBase
    {
        int _MyField;
        public int MyField
        {
            get { return _MyField; }
            set
            {
                if (_MyField != value)
                {
                    _MyField = value;
                    base.OnPropertyChanged("MyField");
                }
            }
        }

        ObservableCollection<ViewClass> _Items;
        public ObservableCollection<ViewClass> Items
        {
            get
            {
                if (_Items == null)
                {
                    _Items = new ObservableCollection<ViewClass>();
                }
                return _Items;
            }
        }
    }