public class Person
{
    private string _name;
    private int _age;

    public Person(string name, int age)
    {
        this._name = name;
        this._age = age;
    }

    public string Name
    {
        get { return this._name; }
        set { this._name = value; }
    }

    public int Age
    {
        get { return this._age; }
        set { this._age = value; }
    }
}

public class PersonCollection : IEnumerable, IEnumerator
{
    private Person[] _collection;

    public PersonCollection(Person[] collection)
    {
        _collection = new Person[collection.Length];

        for (int i = 0; i < collection.Length; i++)
            _collection[i] = collection[i];
    }

    //IEnumerable实现部分

    public IEnumerator GetEnumerator()
    {
        return (IEnumerator)this;
    }

    //IEnumerator实现部分

    private int position = -1;
    public bool MoveNext()
    {
        position++;
        return (position < _collection.Length);
    }

    public void Reset()
    {
        position = -1;
    }

    public object Current
    {
        get
        {
            try
            {
                return _collection[position];
            }
            catch (IndexOutOfRangeException)
            {
                throw new InvalidOperationException();
            }
        }
    }
}

Person[] list = new Person[]{
    new Person("张三",20),
    new Person("李四",21),
    new Person("王五",22)
};
PersonCollection collect = new PersonCollection(list);

foreach (Person person in collect)
    MessageBox.Show(person.Name + "," + person.Age);