using System;

using System.Linq;

​

public class Program

{

    public static void Main()

    {

        Student student1 = new Student();

        if (student1.UnitCodes is not null)

        {

            Console.WriteLine("This student has registered to do some units!");

        }

        else

        {

            student1.UnitCodes = new int[5];

            Console.WriteLine($"This student has registered {student1.UnitCodes.Length}");

            Console.WriteLine($"This student has count {student1.UnitCodes.Count()}");

        }

    }

}

​

public class Student

{

    public int[] UnitCodes {get; set; }

}