IEnumerable、GetEnumerator、IEnumerator的理解

概念文字性的东西，我们就不说了，这里我们来点具体的实例第呀；

实例一：

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

namespace Pratice001
{
   public  class Test:IEnumerable
    {
        private static int count = 12;
        private string[] elements;
        private int ctr = 0; //数组下标的计数器；

        public Test(params string[] initialString)
        {
            elements = new String[8];
            foreach (string s in initialString)
            {
                elements[ctr++] = s; //数据初始化
            }
        }
       public  Test(string initialString, char[] delimiters)
        {
            elements = initialString.Split(delimiters); //不同的方式 进行初始化；
        }

        //实现接口中的方法;
        public IEnumerator GetEnumerator()
        {
            return new ForeachTestEnumerator(this);
        }

        public class ForeachTestEnumerator : IEnumerator
        {
            private int position = -1;
            private Test t;
            public ForeachTestEnumerator(Test t)
            {
                this.t = t;
            }

            //实现接口；
            public object Current
            {
                get
                {
                    return t.elements[position];
                }
            }

            public bool MoveNext()
            {
                if (position < t.elements.Length - 1)
                {
                    position++;
                    return true;
                }
                else
                {
                   return  false;
                }
            }

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

        }

    }

}

实例二：

然后我们再来一个实例！

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];
        }
    }

    IEnumerator IEnumerable.GetEnumerator()
    {
       return (IEnumerator) GetEnumerator();
    }

    public PeopleEnum 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;
    }

    object IEnumerator.Current
    {
        get
        {
            return Current;
        }
    }

    public Person 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);

    }
}

/* This code produces output similar to the following:
 *
 * John Smith
 * Jim Johnson
 * Sue Rabon
 *
 */

最好，跟代码，一步步的调试出来看看的呀；