IEnumerable与IEnumerator区别与应用

public interface IEnumerable
 {
   IEnumerator GetEnumerator();
 }

 public interface IEnumerator
 {
   bool MoveNext();
   void Reset();

   Object Current { get; }
}

 应用:

 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);
     }
 }