单例模式

记录下单例模式，方便以后使用：

    //单例模式
    //包含静态构造函数
    //公开的静态方法——提供对象实例，没有就创建
    //全局唯一静态实例
    public class Singleton
    {
        private static Singleton singleton;
        private static readonly object singletonLock = new object();

        //用于测试
        public string sDBconnection = "";

        private Singleton(string sdb)
        {
            sDBconnection = sdb;
            Console.WriteLine("构造函数初始化！！");
        }

        public static Singleton CreateInstance(string sdb)
        {
            if (singleton == null)
            {
                lock (singletonLock)
                {
                    if (singleton == null)
                    {
                        singleton = new Singleton(sdb);
                    }
                }
            }
            return singleton;
        }
    }

Main，方法中调用：

    static void Main(string[] args)
        {
            Singleton singleton = Singleton.CreateInstance("server=1;database=a");
            Singleton singleton1 = Singleton.CreateInstance("server=2;database=b");
            Singleton singleton2 = Singleton.CreateInstance("server=3;database=c");
            Singleton singleton3 = Singleton.CreateInstance("server=4;database=d");

            Console.WriteLine(singleton.sDBconnection);
            Console.WriteLine(singleton1.sDBconnection);
            Console.WriteLine(singleton2.sDBconnection);
            Console.WriteLine(singleton3.sDBconnection);

            Console.Read();
        }

输出结果：