自定义集合支持使用 foreach循环访问该集合

自定义集合支持使用 foreach循环访问该集合,需要实现 IEnumerable 和 IEnumerator 接口。

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 Example
{
   public static void Demo(System.Windows.Controls.TextBlock outputBlock)
   {
      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)
         outputBlock.Text += p.firstName + " " + p.lastName + "\n";

   }
}

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