C#拾遺系列(6):迭代器

1. 樣本：

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

        /*

        迭代器代碼使用 yield return 語句依次返回每個元素。yield break 將終止迭代。

        可以在類中實現多個迭代器。每個迭代器都必須像任何類成員一樣有唯一的名稱，

        並且可以在 foreach 語句中被用戶端代碼調用，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，這裡返回的是IEnumerable

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

        {

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

            {

                yield return mColor[end-i];

            }

        }

        //在 foreach 迴圈的每次後續迭代（或對 IEnumerator.MoveNext 的直接調用）中，

        //下一個迭代器代碼體將從前一個 yield 語句之後開始，並繼續下一個語句直至到達迭代器體的結尾或遇到 yield break 語句

        public IEnumerable GetMutipleYied()

        {

            yield return "hello";

            yield return "I am";

            yield return "Jack";

            yield return "wang";

        }

    }

}

 

2. 輸出