一个类型要想支持foreach则必须实现IEnumerable，IEnumerator两个接口。

一个类型要想支持foreach则必须实现IEnumerable，IEnumerator两个接口。
// Namespace: System.Collections, Library: BCL
public interface IEnumerable...{
IEnumerator GetEnumerator();
}
// Namespace: System.Collections, Library: BCL
public interface IEnumerator...{
bool MoveNext();
void Reset();
object Current ...{ get; }
}

实例:
using System;
using System.Collections.Generic;
using System.Windows.Forms;
using System.Collections;
namespace Randam
{
public class car
{
string name;
int year;
public car(string str, int num)
{
name = str;
year = num;
}
public string Name
{
get
{
return name;
}
}
}
public class cars : IEnumerator,IEnumerable
{
private car[] carlist;
int position = -1;
//Create internal array in constructor.
public cars()
{
carlist= new car[6]
{
new car("Ford",1992),
new car("Fiat",1988),
new car("Buick",1932),
new car("Ford",1932),
new car("Dodge",1999),
new car("Honda",1977)
};
}
//IEnumerator and IEnumerable require these methods.
public IEnumerator GetEnumerator()
{
return (IEnumerator)this;
}
//IEnumerator
public bool MoveNext()
{
position++;
return (position < carlist.Length);
}
//IEnumerable
public void Reset()
{position = 0;}
//IEnumerable
public object Current
{
get
{
try
{
return carlist[position];
}
catch (IndexOutOfRangeException)
{
throw new InvalidOperationException();
}
}
}
public static void Main()
{
cars cars = new cars();
foreach (car s in cars)
{
Console.WriteLine("car’s value: {0}", s.Name);
}
IEnumerator ienum = (IEnumerator)cars.GetEnumerator();
ienum.Reset();
Console.WriteLine("***************************");
while (ienum.MoveNext())
{
car s = (car)ienum.Current;
Console.WriteLine("car’s value: {0}", s.Name);
}
}
}
}