备忘录模式（Memento）

/*
 * Window系统可能会异常终止，设计一个系统备份程序。类WindowsSystem是
 * 发起人角色(Orignation)，类Memento是备忘录角色(Memento)，类User是
 * 备忘录管理角色(Caretaker)。应用备忘录模式，用C#控制台应用程序实现
 * 该设计。
 */
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace Memento
{
    //Orignation
    class WindowsSystem
    {
        private string systemstate;
        public string SystemState
        {
            get { return systemstate; }
            set { systemstate = value; }
        }
        public Memento SaveState()
        {
            return (new Memento(systemstate));
        }
        public void RecoveryState(Memento memeto)
        {
            this.systemstate = memeto.SystemState;
        }
        public void Show()
        {
            Console.WriteLine("当前系统状态："+systemstate);
        }
    }
    //Memento
    class Memento
    { 
        private string systemstate;
        public Memento(string systemstate)
        {
            this.systemstate = systemstate;
        }
        public string SystemState
        {
            get { return systemstate; }
        }
    }
    //Caretaker
    class User
    {
        private Memento memento;
        public Memento MementoFunc
        {
            get { return memento; }
            set { memento = value; }
        }
    }
    class Program
    {
        static void Main(string[] args)
        {
            //系统正常
            Console.WriteLine("系统启动");
            WindowsSystem ws = new WindowsSystem();
            ws.SystemState = "正常";
            ws.Show();
            //备份
            Console.WriteLine("系统备份");
            User user = new User();
            user.MementoFunc = ws.SaveState();
            //系统崩溃
            Console.WriteLine("系统崩溃");
            ws.SystemState = "崩溃";
            ws.Show();
            //系统恢复
            Console.WriteLine("系统恢复");
            ws.RecoveryState(user.MementoFunc);
            ws.Show();
        }
    }
}