C# Composition

namespace Composition
{
    public class Order
    {
        public int ID;
        public DateTime OrderDate;
        public Address BillingAddress;
        public Address ShippingAddress;
        public OrderItem[] Items;
    }

    public class Address
    {
        public string Street1;
        public string Street2;
        public City City;
        public string PostalCode;
    }

    public class OrderItem
    {
        public string Product;
        public int Quantity;
        public decimal Price;
    }
}