c#自定义泛型类的实现

闲来无事，自己研究了泛型类的简单的使用，
where表示泛型约束，表示泛型类型中的参数只能是car类型，ienumerable是一个接口，一个集合要支持foreach遍历，
必须实现ienumerable接口

public class car
    {
        public string petname;
        public int speed;
        public car(string name, int currentspeed)
        {
            petname = name;
            speed = currentspeed;
        }
        public car() { }
    }
    public class carcollection<t> : ienumerable<t> where t : car
    {
        private list<t> tcars = new list<t>();
        //添加
        public void addcar(t t)
        {
            tcars.add(t);
        }
        //获取其中一个
        public t getcar(int pos)
        {
           return tcars[pos];
        }
        public int count()
        {
            return tcars.count;
        }
        #region ienumerable<t> 成员
        public ienumerator<t> getenumerator()
        {
            return tcars.getenumerator();
        }
        #endregion
        #region ienumerable 成员
        system.collections.ienumerator system.collections.ienumerable.getenumerator()
        {
            return tcars.getenumerator();
        }
        #endregion
    }

 private void button1_click(object sender, eventargs e)
        {
            car car1 = new car("one", 150);
            car car2= new car("two", 50);
            car car3 = new car("three", 150);
            carcollection<car> cars = new carcollection<car>();
            cars.addcar(car1);
            cars.addcar(car2);
            cars.addcar(car3);
            messagebox.show(cars.count().tostring());
            foreach (car item in cars)
            {
                messagebox.show(item.petname+"--"+item.speed.tostring());
            }
        }