练习创建一个单例模式例子

class Au
    {
        private static readonly Au instance = new Au();

        public static Au Instance
        {
            get
            {
                return instance;
            }
        }

        public void Start()
        {
            Console.WriteLine("Start...");
        }

        public void Stop()
        {
            Console.WriteLine("Stop...");
        }
    }