使用迭代器编写自定义IEnumerator <T>

using System;
using System.Collections;
using System.Collections.Generic;

public class CustomEnumerator<T> : IEnumerator<T>
{
    private readonly List<T> _items;
    private int _currentIndex;

    public CustomEnumerator(List<T> items)
    {
        _items = items;
        _currentIndex = -1;
    }

    public bool MoveNext()
    {
        _currentIndex++;
        return _currentIndex < _items.Count;
    }

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

    public T Current
    {
        get
        {
            if (_currentIndex < 0 || _currentIndex >= _items.Count)
            {
                throw new InvalidOperationException("Enumerator is in an invalid state.");
            }

            return _items[_currentIndex];
        }
    }

    object IEnumerator.Current
    {
        get
        {
            return Current;
        }
    }

    public void Dispose()
    {
        // No disposal needed in this example.
    }
}

var items = new List<int> { 1, 2, 3, 4, 5 };
var enumerator = new CustomEnumerator<int>(items);

while (enumerator.MoveNext())
{
    Console.WriteLine(enumerator.Current);
}

1
2
3
4
5