单例模式

 

单例模式特点：

①控制某个类型的实例数量在整个应用程序中为唯一一个。

② 为客户程序提供一个获取该实例的全局访问点。

经典模式写法：

   public class Singleton
    {
        private static Singleton instance;
        private Singleton()
        {

        }
        public static Singleton GetInstance()
        {
            if (instance == null)
            {
                instance = new Singleton();
            }
            return instance;
        }
    }

多线程下的单例模式写法：

 public class Singleton
    {
        private static Singleton instance;
        private static object _lock = new object();
        private Singleton()
        {

        }
        public static Singleton GetInstance()
        {
            if (instance == null)
            {
                lock (_lock)
                {
                    if (instance == null)
                    {
                        instance = new Singleton();
                    }
                }
            }
            return instance;
        }
    }

懒人模式写法：

 public class Singleton
    {
        private static readonly Singleton instance = new Singleton();

        private Singleton()
        {

        }
        public static Singleton GetInstance()
        {
            return instance;
        }
    }