public static void Main(string[] args) { while (true) { Console.WriteLine("Please enter a sum with 2 parts, for example: 3 * 6"); var userInput = Console.ReadLine(); var(isValid, message) = InputParser.Validate(userInput); if (!isValid) { Console.WriteLine($"Invalid sum. {message}"); Console.WriteLine(); continue; } var(number1, number2, sumType) = InputParser.GetSumParts(userInput); var calculator = new Calculator(); decimal sumResult; switch (sumType) { case '+': sumResult = calculator.Add(number1, number2); break; case '-': sumResult = calculator.Deduct(number1, number2); break; case '*': sumResult = calculator.Multiply(number1, number2); break; default: Console.WriteLine("Sum type not implemented."); Console.WriteLine(); continue; } Console.WriteLine(sumResult); Console.WriteLine(); } }