using System;

public class Program

{

    public static void Main()

    {

        var result = new Result() { RegistrationNumber = "test" };

        result = null;

        if (result?.RegistrationNumber?.Contains("test") is true)

        {

            Console.WriteLine("Hello World!");

        }

    }

    public class Result

    {

        public string RegistrationNumber {get;set;}

    }

}