using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace State_VendingMachineExample
{
    internal class Product
    {
        private List<Item> items;

        public Product()
        {
            items = new List<Item>()
            {
                new Item() { Id = 101, Price = 3.50M },
                new Item() { Id = 201, Price = 4.50M },
                new Item() { Id = 301, Price = 4.50M }
            };
        }

        public decimal? GetPrice(int itemId)
        {
            Item item = items.SingleOrDefault(x => x.Id == itemId);

            return item == null ? null : (decimal?)item.Price;
        }

        private class Item
        {
            public int Id { get; set; }
            public decimal Price { get; set; }
        }
    }
}