关于IEnumerable和IEnumerator

Code
IEnumerable的GetEnumerator返回一个实现了IEnumerator接口的对象
实现IEnumerable接口的类，可以支持foreach循环遍历对象的集合元素
using System;
using System.Collections;

public class Person
{
    public Person(string fName, string lName)
    {
        this.firstName = fName;
        this.lastName = lName;
    }

    public string firstName;
    public string lastName;
}

public class People : IEnumerable
{
    private Person[] _people;
    public People(Person[] pArray)
    {
        _people = new Person[pArray.Length];

        for (int i = 0; i < pArray.Length; i++)
        {
            _people[i] = pArray[i];
        }
    }

    public IEnumerator GetEnumerator()
    {
        return new PeopleEnum(_people);
    }
}

public class PeopleEnum : IEnumerator
{
    public Person[] _people;

    // Enumerators are positioned before the first element
    // until the first MoveNext() call.
    int position = -1;

    public PeopleEnum(Person[] list)
    {
        _people = list;
    }

    public bool MoveNext()
    {
        position++;
        return (position < _people.Length);
    }

    public void Reset()
    {
        position = -1;
    }

    public object Current
    {
        get
        {
            try
            {
                return _people[position];
            }
            catch (IndexOutOfRangeException)
            {
                throw new InvalidOperationException();
            }
        }
    }
}

class App
{
    static void Main()
    {
        Person[] peopleArray = new Person[3]
        {
            new Person("John", "Smith"),
            new Person("Jim", "Johnson"),
            new Person("Sue", "Rabon"),
        };

        People peopleList = new People(peopleArray);
        foreach (Person p in peopleList)
            Console.WriteLine(p.firstName + " " + p.lastName);

    }
}
//
C#中使用IEnumerator接口遍历集合!

using System;
using System.Collections.Generic;
using System.Text;
using System.Collections;namespace ConsoleApplication2
{
    class Program
    {
        static void Main(string[] args)
        {
            ArrayList arlist = new ArrayList();
            for (int i = 0; i <= 8; i++)
            {
                arlist.Add(i);
            }
            IEnumerator enumer = arlist.GetEnumerator(2,5);//这句返回从第二个元素起,找5个元素.结果为 2,3,4,5,6.如果此处换为GetEnumerator(),则返回所有
            while (enumer.MoveNext()) //一定要先movenext,不然会有异常
            {
                Console.WriteLine(enumer.Current.ToString());
            }
            Console.ReadLine();
        }          }