以前，如果我们希望构建支持foreach枚举的自定义集合，只能实现IEnumerable接口（可能还有IEnumerator()）,返回值还必须是IEnumerator类型，除此之外还可以通过迭代器来使用构建foreach循环的类型，详细见下链接。

代码

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); } } }

参考：C#中可枚举类型详解

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