static void Main(string[] args) { System.Console.WriteLine(" Please write your Number: "); var input = System.Console.ReadLine(); while (input.All(char.IsNumber) && !string.IsNullOrEmpty(input)) { var number = int.Parse(input); if (number < SpecialRomanKeys.MinRomanValue || number > SpecialRomanKeys.MaxRomanValue) { System.Console.WriteLine($" -> Error: The number should be between {SpecialRomanKeys.MinRomanValue} and {SpecialRomanKeys.MaxRomanValue}. Please Try again.."); } else { try { System.Console.WriteLine($" Result: {BusinessFactory.Service<IRomanBO>().ConvertNumberToRomanNumeral(number)}"); } catch (Exception ex) { System.Console.WriteLine($" -> Error: {ex.Message}"); } } System.Console.WriteLine("---------------------------"); System.Console.WriteLine(" Please write your Number: "); input = System.Console.ReadLine(); } }