1. 示例：

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Collections;

namespace NetTest

{

  public  class TestIteration

    {

        public void Test()

        {

            SevenColor colorIteration = new SevenColor();

            foreach (string p in colorIteration)

            {

                Console.Out.WriteLine(p);

            }

            Console.Out.WriteLine("-------------Desc-------------------");

            foreach (string c in colorIteration.DescColorIteration(1, 5))

            {

                Console.Out.WriteLine(c);

            }

            Console.Out.WriteLine("--------------multi yield---------");

            foreach (string c in colorIteration.GetMutipleYied())

            {

                Console.Out.WriteLine(c);

            }

        }

    }

    public class SevenColor : IEnumerable

    {

        string[] mColor={"red","orange","yellow","green","cyan","blue","purple"};

        #region IEnumerable Members

        /*

        迭代器代码使用 yield return 语句依次返回每个元素。yield break 将终止迭代。

        可以在类中实现多个迭代器。每个迭代器都必须像任何类成员一样有唯一的名称，

        并且可以在 foreach 语句中被客户端代码调用，如下所示：foreach(int x in SampleClass.Iterator2){}

        */

        public IEnumerator GetEnumerator()

        {

            for (int i = 0; i < mColor.Length; i++)

            {

                yield return mColor[i];

            }

        }

        #endregion

        //注意，这里返回的是IEnumerable

        public System.Collections.IEnumerable DescColorIteration(int start, int end)

        {

            for (int i = 0; i <=end; i++)

            {

                yield return mColor[end-i];

            }

        }

        //在 foreach 循环的每次后续迭代（或对 IEnumerator.MoveNext 的直接调用）中，

        //下一个迭代器代码体将从前一个 yield 语句之后开始，并继续下一个语句直至到达迭代器体的结尾或遇到 yield break 语句

        public IEnumerable GetMutipleYied()

        {

            yield return "hello";

            yield return "I am";

            yield return "Jack";

            yield return "wang";

        }

    }

}

2. 输出