C#可遍历的集合

public class Product
{
    /// <summary>
    /// 自增ID
    /// </summary>
    public int ID { get; set; }
    /// <summary>
    /// 主键
    /// </summary>
    public string Code { get; set; }
    /// <summary>
    /// 名称
    /// </summary>
    public string Name { get; set; }
    /// <summary>
    /// 类型
    /// </summary>
    public string Category { get; set; }
    /// <summary>
    /// 价格
    /// </summary>
    public decimal Price { get; set; }
    /// <summary>
    /// 生产日期
    /// </summary>
    public DateTime ProduceDate { get; set; }
    public override string ToString()
    {
        return string.Format("{0}{1}{2}{3}{4}{5}", ID.ToString().PadLeft(2), Category.PadLeft(15), Code.PadLeft(7), Name.PadLeft(17), Price.ToString().PadLeft(4), ProduceDate.ToString("yyyy-M-d").PadLeft(13));
    }
    public static ProductCollection GetSampleCollection()
    {
        ProductCollection collection = new ProductCollection(
            new Product() { ID = 1, Code = "1001", Category = "Red Wine", Name = "Product1" }
            , new Product() { ID = 2, Code = "1002", Category = "Red Wine", Name = "Product2" }
            , new Product() { ID = 3, Code = "1003", Category = "Red Wine", Name = "Product3" }
            , new Product() { ID = 4, Code = "1004", Category = "Red Wine", Name = "Product4" }
            , new Product() { ID = 5, Code = "1005", Category = "Red Wine", Name = "Product5" }
            , new Product() { ID = 6, Code = "1006", Category = "Red Wine", Name = "Product6" }
            , new Product() { ID = 7, Code = "1007", Category = "Red Wine", Name = "Product7" }
        );
        return collection;
    }
}

产品类

public class ProductCollection : IEnumerable<Product>
{
    private List<Product> list = new List<Product>();
    private Hashtable table;
    public ProductCollection()
    {
        table = new Hashtable();
    }
    public ProductCollection(params Product[] array)
    {
        table = new Hashtable();
        foreach (Product item in array)
        {
            this.Add(item);
        }
    }
    public ICollection Keys
    {
        get { return table.Keys; }
    }
    private string getKey(int index)
    {
        if (index < 0 || index > table.Keys.Count) throw new Exception("索引超出了范围");
        string selected = "";
        int i = 0;
        foreach (string key in table.Keys)
        {
            if (i == index)
            {
                selected = key; break;
            }
            i++;
        }
        return selected;
    }
    /// <summary>
    /// 索引器 支持类似于collection[index]这样的访问
    /// </summary>
    /// <param name="index"></param>
    /// <returns></returns>
    public Product this[int index]
    {
        get { string key = getKey(index); return table[key] as Product; }
        set { string key = getKey(index); table[key] = value; }
    }
    private string getKey(string key)
    {
        foreach (string k in table.Keys)
        {
            if (key == k)
            {
                return key;
            }
        }
        throw new Exception("不存在此键值");
    }
    /// <summary>
    /// 索引器 类似于collection[key]这样的访问
    /// </summary>
    /// <param name="key"></param>
    /// <returns></returns>
    public Product this[string key]
    {
        get { string selected = getKey(key); return table[selected] as Product; }
        set { string selected = getKey(key); table.Remove(table[selected]); this.Add(value); }
    }
    /// <summary>
    /// 在末尾添加成员
    /// </summary>
    /// <param name="item"></param>
    public void Add(Product item)
    {
        //确保key不重复
        foreach (string key in table.Keys)
        {
            if (key == item.Code) throw new Exception("产品代码不能重复");
        }
        table.Add(item.Code, item);
    }
    /// <summary>
    /// 在任意位置添加成员
    /// </summary>
    /// <param name="index"></param>
    /// <param name="item"></param>
    public void Insert(int index, Product item) { }
    /// <summary>
    /// 移除某一成员
    /// </summary>
    /// <param name="item"></param>
    /// <returns></returns>
    public bool Remove(Product item)
    {
        return true;
    }
    /// <summary>
    /// 移除某一位置的成员
    /// </summary>
    /// <param name="index"></param>
    /// <returns></returns>
    public bool RemoveAt(int index) { return true; }
    /// <summary>
    /// 清除所有成员
    /// </summary>
    public void Clear() { table.Clear(); }
    public IEnumerator<Product> GetEnumerator()
    {
        return new ProductEnumerator(this);
    }
    IEnumerator IEnumerable.GetEnumerator()
    {
        return new ProductEnumerator(this);
    }
    /// <summary>
    /// 获得集合的成员数量
    /// </summary>
    public int Count { get { return table.Keys.Count; } }
    public class ProductEnumerator : IEnumerator<Product>
    {
        private ProductCollection collection;
        private int index;
        public ProductEnumerator(ProductCollection productCollection)
        {
            this.collection = productCollection;
            index = -1;
        }
        public Product Current { get { return collection[index]; } }
        object IEnumerator.Current { get { return collection[index]; } }
        public void Dispose() { }
        public bool MoveNext()
        {
            index++;
            if (index >= collection.Count) return false;
            else return true;
        }
        public void Reset() { index = -1; }
    }
}

for和foreach都可进行的迭代

ProductCollection pc = Product.GetSampleCollection();
//for (int i = 0; i < pc.Count-1; i++)
//{
//    string line = pc[i].ToString();
//    Console.WriteLine(line);
//}
foreach (string item in pc.Keys)
{
    Console.WriteLine(pc[item]);
}
Console.ReadKey();

测试代码