using System;

​

public class Model 

{

    public string RoutingNumber;

}

​

public class Program

{

    public static void Main()

    {

        var model = new Model {

            RoutingNumber = null

        };

        if (model.RoutingNumber != null && model.RoutingNumber.Length != 9) {

            Console.WriteLine("Validator1: Routing number is invalid!");

        }

        if (model.RoutingNumber?.Length != 9) {

            Console.WriteLine("Validator2: Routing number is invalid!");

        }

        Console.WriteLine("Hello World");

    }

}