using System;

using System.Collections.Generic;

public class Program

{

    /// https://dotnetfiddle.net/DWvT2t

    /// Отрефакторить

    class Product 

    {

        public Cart cart;

        public string name;

        public Product(string name) 

        {

            this.name = name;

        }

        public override string ToString()

        {

            return this.cart.name + ". " + this.name;

        }

        public void Notify(Cart cart)

        {

            this.cart = cart;

        }

    }

    class Cart

    {

        public List<Product> products;

        public string name;

        public Cart(string name)

        {

            this.name = name;

            this.products = new List<Product>();

        }

        public void Add(Product product)

        {

            this.products.Add(product);

            product.Notify(this);

        }

    }

    public static void Main()

    {

        var cart = new Cart("Customer #1");

        var milk = new Product("Milk");

        var bread = new Product("Bread");

        cart.Add(milk);

        cart.Add(bread);

        Console.WriteLine(milk);

        Console.WriteLine(bread);

    }

}