IEnumerable、GetEnumerator、IEnumerator之间的关系。

了解了这些也就明白了遍历的原理，晚安。

 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 = ; 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 = -;

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

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

     public void Reset()
     {
         position = -;
     }

     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[]
         {
             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
  *
  */