ActiveObject模式使用Command模式实现多线程do

参考 《敏捷软件开发 原则、模式与实践》P.141.
原文为java代码，此处为C#代码。

ActiveObject模式是使用Command模式实现多线程的一种古老技术。

using System;
using System.Collections.Generic;
using System.Linq;

namespace ConsoleApp1
{
    public interface Command
    {
        void Execute();
    }

    public class ActiveObjectEngine
    {
        List<Command> commands = new List<Command>();
        public void AddCommand(Command command)
        {
            commands.Add(command);
        }

        public void Run()
        {
            while (commands.Any())
            {
                var command = commands.First();
                commands.Remove(command);
                command.Execute();
            }
        }
    }

    public class SleepCommand : Command
    {
        private readonly long sleepMs;
        private ActiveObjectEngine engine;
        private Command wakeupCommand;
        private bool started = false;
        private DateTime startTime = DateTime.MinValue;

        public SleepCommand(long sleepMs, ActiveObjectEngine engine, Command wakeupCommand)
        {
            this.sleepMs = sleepMs;
            this.engine = engine;
            this.wakeupCommand = wakeupCommand;
        }

        public void Execute()
        {
            var currentTime = DateTime.Now;
            if (!started)
            {
                started = true;
                startTime = currentTime;
                engine.AddCommand(this);
            }
            else if ((currentTime - startTime).TotalMilliseconds < sleepMs)
            {
                engine.AddCommand(this);
            }
            else
            {
                //Console.Write("-");
                engine.AddCommand(wakeupCommand);
            }
        }
    }

    public class DelayTyper : Command
    {
        private long delayMs;
        private char itsChar;
        private static bool stop = false;
        private static ActiveObjectEngine engine = new ActiveObjectEngine();

        static void Main(string[] args)
        {
            var stopCommand = new StopCommand();
            engine.AddCommand(new DelayTyper(100, '1'));
            engine.AddCommand(new DelayTyper(300, '3'));
            engine.AddCommand(new DelayTyper(500, '5'));
            engine.AddCommand(new DelayTyper(700, '7'));
            engine.AddCommand(new SleepCommand(20000, engine, stopCommand));

            engine.Run();
        }

        private class StopCommand : Command
        {
            public void Execute()
            {
                stop = true;
            }
        }

        public DelayTyper(long delayMs, char itsChar)
        {
            this.delayMs = delayMs;
            this.itsChar = itsChar;
        }

        public void Execute()
        {
            Console.Write(itsChar);
            if (!stop)
            {
                DelayAndRepeat();
            }
        }

        private void DelayAndRepeat()
        {
            engine.AddCommand(new SleepCommand(delayMs, engine, this));
        }
    }
}

输出结果示例

1357113115131711315113117153111311517311131511317115311131175131113151173111531113171513111315171311153111731151311131751131115311713115131117315113111531711311513117131511311175311131151317113151131171531113115173111315113171153111311751311131511731115311131715131113151713111531117311513111317511311153117131151311173151131115317113115137