学步园

单件模式，单件意味着唯一，我们创建的类的实例是唯一的。唯一的处理打印机，消息队列，注册表等等.......
UML图：

单件模式看来简单，其实不然。包括什么双重加锁（多线程要求），延迟实例化等等，具体在TerryLee的blog上有详细的描述，本文不再罗嗦。
单件模式没有公开的构造函数，要实现对象的实例化只能依靠静态的GetInstance方法。在GetInstance方法中判断对象是否存在，存在则返回该对象，不存在就实例化一个对象返回。
Dota中时间是唯一的，以下的例子是对白天黑夜的控制，也就是我们的夜魔技能。
测试代码：
            DotaPatternLibrary.Singleton.GameTime gtObj = DotaPatternLibrary.Singleton.GameTime.GetInstance();
            LandpyForm.Form.OutputResult("Game时间类型：" + gtObj.TimeType);
            Thread balanarGamerThread = new Thread(new ThreadStart(BalanarDarkTime));
            Thread akashaGamerThread = new Thread(new ThreadStart(AkashaGetTimeType));
            balanarGamerThread.Start();
            akashaGamerThread.Start();

/// <summary>
        /// 暗夜魔王放大
        /// </summary>
        public void BalanarDarkTime()
        {
            LandpyForm.Form.OutputResult("夜魔(Balanar)大招");
            DotaPatternLibrary.Singleton.GameTime gtObj = DotaPatternLibrary.Singleton.GameTime.GetInstance();
            gtObj.TimeType = DotaPatternLibrary.Singleton.TimeTypeValue.Evening;
            for (int i = 1; i < 5; i++)
            {
                Thread.Sleep(2000);
                LandpyForm.Form.OutputResult("时间过去" + i * 2 + "秒");
            }
            LandpyForm.Form.OutputResult("夜魔(Balanar)大招时间到");
            DotaPatternLibrary.Singleton.GameTime gtObjNew = DotaPatternLibrary.Singleton.GameTime.GetInstance();
            gtObjNew.TimeType = DotaPatternLibrary.Singleton.TimeTypeValue.DayTime;
        }

        /// <summary>
        /// 痛苦女王获得时间类型
        /// </summary>
        public void AkashaGetTimeType()
        {
            for (int i = 1; i < 4; i++)
            {
                Thread.Sleep(2000);
                DotaPatternLibrary.Singleton.GameTime gtObj = DotaPatternLibrary.Singleton.GameTime.GetInstance();
                LandpyForm.Form.OutputResult("痛苦女王(Akasha)获得时间：" + gtObj.TimeType);
                Thread.Sleep(3000);
            }
        }

完整代码：

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

using DotaPatternLibrary.Attribute;

namespace DotaPatternLibrary.Singleton
{
    class Singleton
    {
        public static object lockObj = new object();
        private static Singleton singleton;

        private Singleton()
        {
        }

        public static Singleton GetInstance()
        {
            lock (lockObj)
            {
                if (singleton == null)
                {
                    singleton = new Singleton();
                }
            }
            return singleton;
        }
    }

    public class TimeTypeValue
    {
        public const string DayTime = "DayTime(白天)";
        public const string Evening = "Evening(夜晚)";
    }

    public class GameTime
    {
        private static object lockObj = new object();
        private static GameTime gameTime;
        private string _timeType;

        public string TimeType
        {
            get { return _timeType; }
            set { _timeType = value; }
        }

        private GameTime()
        {
            this._timeType = TimeTypeValue.DayTime;
        }

        public static GameTime GetInstance()
        {
            lock (lockObj)
            {
                if (gameTime == null)
                {
                    gameTime = new GameTime();
                }
            }
            return gameTime;
        }
    }
}