static void Main(string[] args) { string command = "add 1,4,5"; ICalc cal = null; string result = null; CalcFactory cf = new CalcFactory(); cal = cf.GetObject("add1"); //Wrong command //cal = cf.GetObject(cmd.Substring(0,cmd.Split(' ')[0].Length)); //correct command if (cal != null) { Console.WriteLine("No command found"); result = cal.Calculation(command); Console.WriteLine($"output of add command is {result}"); } cal = cf.GetObject(command.Substring(0, command.Split(' ')[0].Length)); if (cal != null) { Console.WriteLine("No command found"); result = cal.Calculation(command); Console.WriteLine($"output of add command is {result}"); } Console.Read(); }