作者：未知 来源：月光软件站 加入时间：2005-2-28　月光软件站

using System;

namespace DesignPatters.Singleton
{
    public class Singleton
    {
        public static Singleton Instance()
        {
            if (_instance == null)
            {
                lock (typeof(Singleton))
                {
                    if (_instance == null)
                    {
                        _instance = new Singleton();
                    }
                }
            }

            return _instance;
        }

        public int NextValue()
        {
            return ++count;
        }

        protected Singleton(){}
        private static volatile Singleton _instance = null;
        private int count = 0;
    }

    public class MainClient
    {
        [STAThread]
        static void Main()
        {
            Singleton sg1 = Singleton.Instance();

            for (int i = 0; i < 20; i++)
                Console.WriteLine("Next Value: {0}",
                        sg1.NextValue() + " - sg1");

            Singleton sg2 = Singleton.Instance();

            Console.WriteLine("Next Value: {0}",
                    sg2.NextValue() + " - sg2");
        }
    }
}

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