public interface IIterator
{
    void First();
    string Next();
    bool IsDone();
    string Current();
}

public class IWannaIterate : IIterator
{
    private List<string> _list;
    private int position;
    public IWannaIterate(List<string> list)
    {
      Console.WriteLine("我要感谢IIterator，有了它我才可以迭代");
      _list = list;
      position = 0;
    }
    public void First()
    {
      position = 0;
    }
    public string Next()
    {
      return _list[position++];
    }
    public bool IsDone()
    {
      return position >= _list.Count;
    }
    public string Current()
    {
      return _list[position];
    }
}

public interface IManagement
{
    IIterator CreateIterator();
}

public class MyUserManagement : IManagement
{
    private List<string> _users;
    public MyUserManagement()
    {
      _users = new List<string>();
      _users.Add("hello");
      _users.Add("world");
      _users.Add("nice");
    }
    public IIterator CreateIterator()
    {
      return new IWannaIterate(_users);
    }
}

public class MyBookManagement : IManagement
{
    private List<string> _books;
    public MyBookManagement()
    {
      _books = new List<string>();
      _books.Add("美丽世界");
      _books.Add("你好吗");
    }
    public IIterator CreateIterator()
    {
      return new IWannaIterate(_books);
    }
}

class Program
{
    static void Main(string[] args)
    {
      IManagement magageA = new MyUserManagement();
      IManagement manageB = new MyBookManagement();
      IIterator iteratorA = magageA.CreateIterator();
      IIterator iteratorB = manageB.CreateIterator();
      Console.WriteLine("打印出的user列表");
      PrintList(iteratorA);
      Console.WriteLine();
      Console.WriteLine("打印出book列表");
      PrintList(iteratorB);
      Console.ReadKey();
    }
    private static void PrintList(IIterator iterator)
    {
      while (!iterator.IsDone())
      {
        Console.WriteLine(iterator.Next());
      }
    }
}