迭代 yield

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Collections;

namespace MyArray
{
    class Program
    {
      
        static void Main(string[] args)
        {
            MyNames names = new MyNames();

            Console.WriteLine("默认");
            foreach (string name in names)
            {
                Console.WriteLine(name);
            }

            Console.WriteLine("倒序");
            foreach (string name in names.Reverse())
            {
                Console.WriteLine(name);
            }

            Console.WriteLine("截取");
            foreach (string name in names.Subset(2, 2))
            {
                Console.WriteLine(name);
            }
            Console.Read();
        }  
    }

  public   class MyNames
    {
      string[] names = { "liang", "zhnag", "li", "chen" };
      public IEnumerator GetEnumerator()
      {
          for (int i = 0; i < 4; i++)
          {
              yield return names[i];
          }
      }

      public IEnumerable Reverse()
      {
          for (int i = 3; i >=0; i--)
          {
              yield return names[i];
          }
      }
      /// <summary>
      ///  用Subset()方法搜索迭代子集
      /// </summary>
      /// <param name="index">起始索引</param>
      /// <param name="length">返回元素的个数</param>
      /// <returns></returns>
      public IEnumerable Subset(int index, int length)
      {
          for (int i = 0; i < index + length; i++)
          {
              yield return names[i];
          }
      }
    }
}