自定义类支持foreach

建议使用yield语句简化迭代

using System;
using System.Collections;

namespace 自定义类实现foreach
{
    class A
    {
        int[] w;
        public A(int d)
        {
            w = new int[d];
        }
        public IEnumerator GetEnumerator()
        {
            for (int i = ; i < w.Length; i++)
            {
                yield return i;
            }
        }
    }
    class Program
    {
        static void Main(string[] args)
        {
            A a = new A();
            foreach (var i in a)
            {
                Console.WriteLine(i);
            }

        }
    }
}