public static Portfolio Open(PortfolioId id, AccountType accountType, Money initialDeposit)
        {
            if (initialDeposit < MinimumPortfolioBalance)
            {
                throw new InvalidOperationException(String.Format("The intial deposit of {0} is lower than the require a minimum of {1}", initialDeposit, MinimumPortfolioBalance));
            }

            var portfolio = new Portfolio(id);

            portfolio.OpenAccount(accountType);
            portfolio.CreditAccount(accountType, initialDeposit);

            return(portfolio);
        }
 protected Portfolio(PortfolioId id)
     : base(id)
 {
     accounts = new HashSet <Account>();
     isOpen   = true;
 }