实现类对象的枚举遍历

/*-------------实现类对象的枚举遍历
 如果希望枚举一个可枚举对象（实现IEnumerable接口）的元素，就可以通过IEnumerable接口的GetEnumerator()
 * 方法从可枚举对象请求一个枚举器，接下来可以用枚举器的IEnumerator.MoveNext(),Reset,Current方法遍历。
 * public interface IEnumerable
 * {
 *    IEnumerator GetEnumerator();
 * }
 * public interface IEnumerator
 * {
 *    object Current{get;}
 *    bool MoveNext();
 *    void Reset();
 * }
 */
    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;
       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();
             }
          }
       }
    }

   调用：
   public static void ForeachDisplay()
   {
            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);
  }