public HomeController(RefundCommandHandler refundCommandHandler, BuyCommandHandler buyCommandHandler)
        {
            Contract.Requires(refundCommandHandler != null);
            Contract.Requires(buyCommandHandler != null);

            _refundCommandHandler = refundCommandHandler;
            _buyCommandHandler    = buyCommandHandler;
        }
        public HomeController(RefundCommandHandler refundCommandHandler, BuyCommandHandler buyCommandHandler)
        {
            Contract.Requires(refundCommandHandler != null);
            Contract.Requires(buyCommandHandler != null);

            _refundCommandHandler = refundCommandHandler;
            _buyCommandHandler = buyCommandHandler;
        }