转：C#中Undo/Redo的一个简易实现

一个比较常见的改进用户体验的方案是用Redo/Undo来取代确认对话框，由于这个功能比较常用，本文简单的给了一个在C#中通过Command模式实现Redo/Undo方案的例子，以供后续查询。

class Program
{
    static void Main(string[] args)
    {
        var cmds = new CommandManager();
        while (true)
        {
            var key = Console.ReadKey(true);
            if (key.KeyChar >= '0' && key.KeyChar <= '9')
            {
                cmds.DoNewCommand(key.KeyChar.ToString(), () => Console.WriteLine("process " + key.KeyChar), () => Console.WriteLine("redo " + key.KeyChar));
            }
            else
            {
                if (key.Modifiers.HasFlag(ConsoleModifiers.Control) && (key.Key == ConsoleKey.Z))
                    cmds.UnDo();
                else if (key.Modifiers.HasFlag(ConsoleModifiers.Control) && (key.Key == ConsoleKey.Y))
                    cmds.ReDo();
            }
        }
    }
}

class CommandManager
{
    #region Command定义
    public class Command
    {
        string name;
        Action action;
        Action unDoAction;

        internal Command(string name, Action action, Action unDoAction)
        {
            this.name = name;
            this.action = action;
            this.unDoAction = unDoAction;
        }

        internal void Do() { action(); }
        internal void UnDo() { unDoAction(); }

        public override string ToString()
        {
            return name.ToString();
        }
    }
    #endregion

    public Stack<Command> ReDoActionStack { get; private set; }
    public Stack<Command> UnDoActionStack { get; private set; }

    public CommandManager()
    {
        ReDoActionStack = new Stack<Command>();
        UnDoActionStack = new Stack<Command>();
    }

    public void DoNewCommand(string name, Action action, Action unDoAction)
    {
        var cmd = new Command(name, action, unDoAction);
        UnDoActionStack.Push(cmd);
        ReDoActionStack.Clear();
        cmd.Do();
    }

    public void UnDo()
    {
        if (!CanUnDo)
            return;

        var cmd = UnDoActionStack.Pop();
        ReDoActionStack.Push(cmd);
        cmd.UnDo();
    }

    public void ReDo()
    {
        if (!CanReDo)
            return;

        var cmd = ReDoActionStack.Pop();
        UnDoActionStack.Push(cmd);
        cmd.Do();
    }

    public bool CanUnDo { get { return UnDoActionStack.Count != 0; } }
    public bool CanReDo { get { return ReDoActionStack.Count != 0; } }
    //public IEnumerable<Command> Actions { get { return ReDoActionStack.Reverse().Concat(UnDoActionStack); } }
}

代码