Anemic Shopping Cart

   public class CartService : ICartService
    {
        private readonly ICartRepository _cartRepository;
        private readonly IProductRepository _productRepository;

        public CartService(ICartRepository cartRepository, IProductRepository productRepository)
        {
            _cartRepository = cartRepository;
            _productRepository = productRepository;
        }

        public void AddToCart(long cartId, long productId, int quantity)
        {
            var cart = _cartRepository.Get(cartId);
            if (cart == null)
                throw new ArgumentException("Cart not found. CartId: " + cartId);
            var product = _productRepository.Get(productId);
            if (product == null)
                throw new ArgumentException("Product not found. ProductId: " + productId);
            var cartItem = new CartItem(cart.Id, productId, quantity);
            cart.Items.Add(cartItem);
            _cartRepository.Save(cart);
        }
    }
    public class Customer
    {
        public long Id { get; private set; }
        public string Name { get; private set; }
    }

    public class CartItem
    {
        public CartItem(long id, long productId, int quantity)
        {
            Id = id;
            ProductId = productId;
            Quantity = quantity;
        }

        public long Id { get; private set; }
        public long CartId { get; private set; }
        public long ProductId { get; private set; }
        public int Quantity { get; set; }
    }

    public class Cart
    {
        public Cart()
        {
            Items = new List<CartItem>();
        }
        public long Id { get; private set; }
        public long CustomerId { get; set; }
        public List<CartItem> Items { get; set; }
    }