public virtual IEnumerable<Market> GetMarkets()
{
var belgium = new Country("Belgium", "BE");
var antwerp = new City("Antwerp", "2000", belgium);
yield return new Market(new Address("Groenplaats", antwerp));
yield return new Market(new Address("Sint-Jansplein", antwerp));
}
public City(string name, string postalCode, Country country)
{
_name = name;
_postalCode = postalCode;
_country = country;
}