using System;

public class Program

{

    public class Thing

    {

        public int Dis { get; set; }

        public int Dat { get; set; }

    }

    public static void Main()

    {

        Thing thang = new Thing();

        thang.Dis = 17;

        thang.Dat = 42;

        if (thang?.Dis == 17 || thang.Dat == 17)

        {

            Console.WriteLine("Seventeen!");

        }

        Thing thing = null;

        if (thing?.Dis == 17 || thing.Dat == 17)

        {

            Console.WriteLine("Seventeen?!");

        }

    }

}