看到个委托事件问题

 1 class Program
 2     {
 3         static void Main(string[] args)
 4         {
 5             CarEven car = new CarEven();
 6             car.MaxSpeed = 180;
 7             UpSpeed up = new UpSpeed(car);
 8             DownSpeed down = new DownSpeed(car);
 9             for(int i=0;i<205;i++){
10                 car.Speed();
11             }
12             Console.ReadLine();
13         }
14     }
15     //速度
16     public delegate void SpeedEventHandler();
17 
18     public class CarEven{
19         //速度事件
20         public event SpeedEventHandler SpeedEvent;
21         public int CurrSpeed { get; set; }
22         public int MaxSpeed { get; set; }
23 
24         public CarEven()
25         {
26             CurrSpeed = 0;
27         }
28 
29         public void Speed()
30         {
31             SpeedEvent();
32         }
33     }
34 
35     public class UpSpeed{
36         CarEven car;
37         public UpSpeed(CarEven car)
38         {
39             this.car = car;
40             car.SpeedEvent +=new SpeedEventHandler(car_SpeedEvent); // 订阅事件
41         }
42         void car_SpeedEvent()
43         {
44             if (car.CurrSpeed < car.MaxSpeed)
45             {
46                 Console.WriteLine("踩下油门，当前速度：{0}", car.CurrSpeed);
47                 car.CurrSpeed++;
48             }
49         }
50     }
51 
52     public class DownSpeed{
53         CarEven car;
54         public DownSpeed(CarEven car)
55         {
56             this.car = car;
57             car.SpeedEvent +=new SpeedEventHandler(car_SpeedEvent); // 订阅事件
58         }
59         void car_SpeedEvent()
60         {
61             if (car.CurrSpeed >= car.MaxSpeed)
62             {
63                 Console.WriteLine("踩下刹车，当前速度：{0}", car.CurrSpeed);
64                 car.CurrSpeed = car.CurrSpeed - 10;
65             }
66         }
67     }