c# delegate中的一些问题
class Program
    {
        static void Main(string[] args)
        {
            var car = new Car(15);
            new Alerter(car); \\这个是什么意思呢
            car.Run(120);
        }
    }

    class Car
    {
        public delegate void Notify(int value);
        public event Notify notifier;

        private int petrol = 0;
        public int Petrol
        {
            get { return petrol; }
            set
            {
                petrol = value;
                if (petrol < 10)  //当petrol的值小于10时，出发警报
                {
                    if (notifier != null)
                    {
                        notifier.Invoke(Petrol);
                    }
                }
            }
        }

        public Car(int petrol)
        {
            Petrol = petrol;
        }

        public void Run(int speed)
        {
            int distance = 0;
            while (Petrol > 0)
            {
                Thread.Sleep(500);
                Petrol--;
                distance += speed;
                Console.WriteLine("Car is running...