CSharp: Composite Pattern in donet 6

     /// <summary>
    /// 组合模式 Composite Pattern 亦称： 对象树、Object Tree、Composite Pattern
    /// </summary>
    public abstract class Gift
    {

        /// <summary>
        /// 
        /// </summary>
        protected readonly string _description;
        /// <summary>
        /// 
        /// </summary>
        protected decimal _price;
        /// <summary>
        /// 
        /// </summary>
        /// <param name="description"></param>
        /// <param name="price"></param>
        protected Gift(string description, decimal price)
        {
            _description = description;
            _price = price;
        }
        /// <summary>
        /// 
        /// </summary>
        /// <returns></returns>
        public abstract decimal CalculatePrice();
    }


   /// <summary>
    /// 组合模式 Composite Pattern 亦称： 对象树、Object Tree、Composite Pattern
    /// </summary>
    public interface IGiftOperations
    {

        /// <summary>
        /// 
        /// </summary>
        /// <param name="gift"></param>
        void Add(Gift gift);
        /// <summary>
        /// 
        /// </summary>
        /// <param name="gift"></param>
        void Remove(Gift gift);
    }

 /// <summary>
    /// 组合模式 Composite Pattern 亦称： 对象树、Object Tree、Composite Pattern
    /// </summary>
    public class CompositeGift : Gift, IGiftOperations
    {
        /// <summary>
        /// This collection can store simple as well as composite gifts.
        /// </summary>
        private readonly List<Gift> _gifts;
        /// <summary>
        /// 
        /// </summary>
        /// <param name="description"></param>
        public CompositeGift(string description)
            : base(description, 0)
        {
            _gifts = new List<Gift>();
        }
        /// <summary>
        /// 
        /// </summary>
        /// <param name="gift"></param>
        public void Add(Gift gift) =>
            _gifts.Add(gift);
        /// <summary>
        /// 
        /// </summary>
        /// <param name="gift"></param>
        public void Remove(Gift gift) =>
            // Consider using HashSet or Dictionary if you need remove an item from a collection.
            _gifts.Remove(gift);
        /// <summary>
        /// 
        /// </summary>
        /// <returns></returns>
        public override decimal CalculatePrice()
        {
            Console.WriteLine($"'{_description}' 包含以下产品及价格:");
            _price = _gifts.Sum(gift => gift.CalculatePrice());

            return _price;
        }
    }


/// <summary>
    /// 组合模式 Composite Pattern 亦称： 对象树、Object Tree、Composite Pattern
    /// </summary>
    public class SimpleGift : Gift
    {

        /// <summary>
        /// 
        /// </summary>
        /// <param name="description"></param>
        /// <param name="price"></param>
        public SimpleGift(string description, decimal price)
            : base(description, price)
        {
        }
        /// <summary>
        /// 
        /// </summary>
        /// <returns></returns>
        public override decimal CalculatePrice()
        {
            Console.WriteLine($"'{_description}' with the price of {_price:C}");
            return _price;
        }
    }


 /// <summary>
    ///  组合模式 Composite Pattern 亦称： 对象树、Object Tree、Composite Pattern
    /// </summary>
    public static class GiftExecutor
    {

        /// <summary>
        /// /
        /// </summary>
        public static void Execute()
        {
            ConsoleExtension.WriteSeparator("组合模式 Composite Pattern:  Gift demo");

            var smartWatchGift = new SimpleGift("智能手表 Smart watch", 200);
            var smartWatchPrice = smartWatchGift.CalculatePrice();
            Console.WriteLine($"智能手表礼品总价: {smartWatchPrice:C}");

            Console.WriteLine();

            var familyGift = new CompositeGift("家庭的礼物");
            var dadsGift = new SimpleGift("钓鱼竿Fishing rod", 50);
            var momsGift = new SimpleGift("项链Necklace", 80);
            var childrenGift = new CompositeGift("孩子们的礼物Children gift");
            childrenGift.Add(new SimpleGift("士兵玩具Soldier toy", 40));
            childrenGift.Add(new SimpleGift("芭比玩具Barbie toy", 50));

            familyGift.Add(dadsGift);
            familyGift.Add(momsGift);
            familyGift.Add(childrenGift);

            var familyGiftPrice = familyGift.CalculatePrice();
            Console.WriteLine($"家庭礼物总价: {familyGiftPrice:C}");
        }
    }

　　调用：、

            Geovin.Du.DuComposite.DuGift.GiftExecutor.Execute();
            Console.WriteLine();

输出：

组合模式 Composite Pattern:  Gift demo
--------------------------------------------------
'智能手表 Smart watch' with the price of ￥200.00
智能手表礼品总价: ￥200.00

'家庭的礼物' 包含以下产品及价格::
'钓鱼竿Fishing rod' with the price of ￥50.00
'项链Necklace' with the price of ￥80.00
'孩子们的礼物Children gift' 包含以下产品及价格::
'士兵玩具Soldier toy' with the price of ￥40.00
'芭比玩具Barbie toy' with the price of ￥50.00
家庭礼物总价: ￥220.00