关于C# 设计模式 Singleton 单例模式

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

///Singleton（单件）模式用于保证一个类仅有一个实例，并提供一个访问该实例的全局访问点。
///add by jzh 2007-04-15
namespace DesignPattern
{
    class Singleton
    {
        private static Singleton _instance;

        public static Singleton Instance()
        {
            if (_instance == null)
                _instance = new Singleton();
            return _instance;
        }
        protected Singleton() { }

        private int x = 0;
        public void SetX(int newVal) { x = newVal; }
        public int GetX() { return x; }
    }

    public class Client
    {
        public static void Main(string[] args)
        {
            int val;
            Singleton FirstSingleton = Singleton.Instance();
            Singleton SecondSingleton = Singleton.Instance();

            // 重新得到
            FirstSingleton.SetX(4);
            Console.WriteLine("赋值, set x to 4");

            val = SecondSingleton.GetX();
            Console.WriteLine("取值, value retrieved = {0}", val);

            Console.ReadLine();
        }
    }
}