IEnumerable接口和IEnumerator接口是.NET中非常重要的接口，二者有何区别？
1. 简单来说IEnumerable是一个声明式的接口，声明实现该接口的类就是“可迭代的enumerable”,但并没用说明如何实现迭代器(iterator).其代码实现为：
public interface IEnumerable
{ IEnumerator GetEnumerator(); } 2. 而IEnumerator接口是实现式接口，它声明实现该接口的类就可以作为一个迭代器iterator.其代码实现为：public interface IEnumerator
{ object Current { get; }bool MoveNext();
void Reset(); }3.一个collection要支持Foreach进行遍历，就必须实现IEnumerable,并一某种方式返回迭代器对象:IEnumerator.
那么又如何实现这两个接口呢？ 其代码如下：
假设有一个Person类，其有两个属性FirstName和LastName
public class Person
{ public string FirstName { get; set; } public string LastName { get; set; } public Person(string firstName, string lastName) { this.FirstName = firstName; this.LastName = lastName; } }另外通过People类来实现IEnumerable和IEnumerator接口.
//实现IEnumerable接口
public class People :IEnumerable
{
public Person [] pers;
public People(Person [] ps)
{
this.pers = ps;
}
public IEnumerator GetEnumerator()
{
//foreach(Person p in pers)
// {
// yield return p;
// }
return new People1(pers);
}
}
//实现IEnumerator接口
public class People1 : IEnumerator
{ public Person[] pers; public People1(Person[] per) { this.pers = per; } int position = -1;public bool MoveNext()
{ position++; return position < pers.Length; } public void Reset() { position=-1; } public object Current { get { try { return pers[position]; } catch(IndexOutOfRangeException ex) { throw new InvalidOperationException(); } } } }