public void StockUp(string nameString, string priceString, string amountString) { string name = nameString.Trim().ToLower(); int price = _inputValidation.ConvertPrice(priceString); int amount = _inputValidation.ConvertAmount(amountString); string stockUpMsg = ""; for (int i = 0; i < amount; i++) { ProductsList.Add(new Products() { ProductName = name, Price = price }); } if (amount == 1) { stockUpMsg += $"{amount} {name} was added to the shop with the price of {price} $"; } else { stockUpMsg += $"{amount} {name} products ware added to the shop with the price of {price} $"; } _service.WriteResult(stockUpMsg); }