private Error SellStocks(StockEvent e)
        {
            Stock_M s = _mainModel.Stocks.Find((stock) => stock.Tag == e.Name);

            if (s != null)
            {
                BuyOrSell_M bos = _currentPortfolio.CurrentlyHeld().Find(b => b.StockName == s.Name);
                if (e.Amount > bos.Quantity)
                {
                    return(new Error("Selling too many stocks"));
                }
                _currentPortfolio.SellStock(s, e.Amount);
            }
            Broadcast(new PortfolioEvent("portfolio", _currentPortfolio.Name));
            return(Error.None);
        }
        private Error BuyStocks(StockEvent e)
        {
            Stock_M s = _mainModel.Stocks.Find((stock) => stock.Tag == e.Name);

            if (s != null)
            {
                if (_currentPortfolio.CurrentlyHeld().Exists(b => b.StockName == s.Name))
                {
                    return(new Error("Cannot buy stock you already own"));
                }
                try
                {
                    _currentPortfolio.PurchaseStock(s, e.Amount);
                }
                catch (ArgumentException err)
                {
                    return(new Error(err.Message));
                }
            }
            Broadcast(new PortfolioEvent("portfolio", _currentPortfolio.Name));
            return(Error.None);
        }