Presentation Model (MVVM) Good Practices

using System;
using System.Collections.Generic;
using System.Text;
using App.Core;
using System.Threading;
using System.ComponentModel;

namespace App.Data
{
    public class DummyDao<T> : IDao<T>
    {
        List<T> _storage = new List<T>();

        #region IDao<T> Members

        public void SaveOrUpdate(T item)
        {
            if (!_storage.Contains(item))
            { 
                _storage.Add(item);
                OnChange(item, ListChangedType.ItemAdded);
            }
            else
                OnChange(item, ListChangedType.ItemChanged);
        }

        public void Remove(T item)
        {
            _storage.Remove(item);
            OnChange(item, ListChangedType.ItemDeleted);
        }

        public T GetByKey(int key) 
        {
            return _storage[key];
        }

        public IList<T> SelectAll()
        {
            return _storage;
        }

        public event ListChangedEventHandler Changed;

        protected void OnChange(T item, ListChangedType changeType)
        {
            if (Changed != null)
                Changed(item, new ListChangedEventArgs(changeType, _storage.IndexOf(item)));
        }

        #endregion

    }
}