使用 foreach 访问集合类问题

using System.Collections;

// Declare the Tokens class:
public class Tokens : IEnumerable
{
    private string[] elements;

    Tokens(string source, char[] delimiters)
    {
        // Parse the string into tokens:
        elements = source.Split(delimiters);
    }

    // IEnumerable Interface Implementation:
    //   Declaration of the GetEnumerator() method
    //   required by IEnumerable
    public IEnumerator GetEnumerator()
    {
        return new TokenEnumerator(this);
    }

    // Inner class implements IEnumerator interface:
    private class TokenEnumerator : IEnumerator
    {
        private int position = -1;
        private Tokens t;

        public TokenEnumerator(Tokens t)
        {
            this.t = t;
        }

        // Declare the MoveNext method required by IEnumerator:
        public bool MoveNext()
        {
            if (position < t.elements.Length - 1)
            {
                position++;
                return true;
            }
            else
            {
                return false;
            }
        }

        // Declare the Reset method required by IEnumerator:
        public void Reset()
        {
            position = -1;
        }

        // Declare the Current property required by IEnumerator:
        public object Current
        {
            get
            {
                return t.elements[position];
            }
        }
    }

    // Test Tokens, TokenEnumerator
    static void Main()
    {
        // Testing Tokens by breaking the string into tokens:
        Tokens f = new Tokens("This is a sample sentence.", new char[] {' ','-'});

        foreach (string item in f)
        {
            System.Console.WriteLine(item);
        }
    }
}
我很奇怪的是当第一次运行到foreach (string item in f)这句的是   停到了f上面之后直接调运了
public IEnumerator GetEnumerator()这个方法 position=-1;   之后运行到in的时候就直接运行了public bool MoveNext()
方法了  然后就开始循环了  是。net设计时候就是这样默认的么？ --------------------编程问答-------------------- 是的，你可以理解成遍历一个链表。

补充：.NET技术 ,  C#