C# 备忘录模式（Memento）

获取目标对象的当前内部状态，并将状态保存在对象外部，以后可以从将目标对象恢复到保存时的状态。代码如下：

using System;
using System.Collections.Generic;
using System.Text;
using System.Windows.Forms;


namespace DesignMode.Memento
{
    public class MyAim
    {
        private string _state1;
        private int _state2;
        private decimal _state3;

        public decimal State3
        {
            get { return _state3; }
            set { _state3 = value; }
        }

        public int State2
        {
            get { return _state2; }
            set { _state2 = value; }
        }
        public string State1
        {
            get { return _state1; }
            set { _state1 = value; }
        }

        public MyAim()
        {
            this._state1 = "1";
            this._state2 = 1;
            this._state3 = 1.0M;
        }

        public void SetState()
        {
            this._state1 = "2";
            this._state2 = 2;
            this._state3 = 2.0M;
        }

        public void DisplayState()
        {
            MessageBox.Show(" state1:" + State1 + "\n state2:" + State2 + "\n state3:" + State3);
        }

        //保存当前状态
        public MyMemento SaveState()
        {
            return new MyMemento(_state1, _state2, _state3);
        }

        //恢复状态
        public void RecoveryState(MyMemento myMemento)
        {
            this._state1 = myMemento.State1;
            this._state2 = myMemento.State2;
            this._state3 = myMemento.State3;
        }
    }

    //备忘录类，用于保存当前状态
    public class MyMemento
    {
        private string _state1;
        private int _state2;
        private decimal _state3;

        public MyMemento(string state1,int state2,decimal state3)
        {
            this._state1 = state1;
            this._state2 = state2;
            this._state3 = state3;
        }

        public MyMemento()
        { 
        }

        public decimal State3
        {
            get { return _state3; }
            set { _state3 = value; }
        }

        public int State2
        {
            get { return _state2; }
            set { _state2 = value; }
        }
        public string State1
        {
            get { return _state1; }
            set { _state1 = value; }
        }
    }


    //将备忘录对象保存到外部类
    public class ExternalSave
    {
        private MyMemento myMemento;

        public MyMemento MyMemento
        {
            get { return myMemento; }
            set { myMemento = value; }
        }
    }


}

客户端代码：

        private void btn_Memento_Click(object sender, EventArgs e)
        {
            
            MyAim aim = new MyAim();
            aim.DisplayState();

            ExternalSave external = new ExternalSave();
            external.MyMemento = aim.SaveState();

            aim.SetState();
            aim.DisplayState();

            aim.RecoveryState(external.MyMemento);
            aim.DisplayState();

        }