C#使用yield关键字构建迭代器详解

 public class Car  {    //内部状态数据    public int CurentSpeed;    public int MaxSpeed;    public string name;    //汽车能不能用    private bool carIsdead;    //类构造函数    public Car() { }    public Car(string name, int currentspeed, int maxspeed = 100)    {      this.name = name;      this.CurentSpeed = currentspeed;      this.MaxSpeed = maxspeed;    }    //定义委托类型    public delegate void CarEngineHandler(string msdForCar);    //定义每个委托类型的成员变量    private CarEngineHandler listOfhandlers;    //向调用者添加注册函数    public void RegisterWithCarEngine(CarEngineHandler methodTocall)    {      if (listOfhandlers == null)        listOfhandlers = methodTocall;      else        listOfhandlers += methodTocall;//支持多路广播    }    //实现Accelerate()方法    public void Accelerate(int delta)    {      if (carIsdead)      {        if (listOfhandlers != null)        {          listOfhandlers("sorry,this car is dead");        }      }      else      {        CurentSpeed += delta;        //不能超过最大速度        if (5 == (MaxSpeed - CurentSpeed) && listOfhandlers != null)        {          listOfhandlers("this speed is nearly to the maxspeed");        }        if (CurentSpeed > MaxSpeed)        {          carIsdead = true;        }        else          Console.WriteLine("current speed:{0}", CurentSpeed);      }    }  }  public class Garage : IEnumerable  {    private Car[] garage = new Car[3];    public Garage()    {      garage[0] = new Car("a", 10);      garage[1] = new Car("b", 13);      garage[2] = new Car("c", 14);    }    public Enumerator GetEnumerator()    {      //返回数组对象的IEnumerator      //return garage.GetEnumerator();      //用yield关键字构建迭代器方法      foreach (Car c in garage)      {        //当yield return语句执行后，当前位会被        //保存下来，下一次执行会从当前位开始        yield return c;      }    }  }  class Program  {    static void Main(string[] args)    {      Garage g = new Garage();      foreach (Car c in g)      {        Console.WriteLine("car name:{0}", c.name);      }    }  }