#nullable enable

​

​

using System;

using System.Collections.Generic;

public class C

{

    public static void Main()

    {

    Console.WriteLine("foo");

    var student = new Student("asdf",new List<string>(){"asdf","ags",null});

        Console.WriteLine($"Student name is: {student?.Name}");

        Console.WriteLine($"First enrolled course is: {student?.Courses?[2]}");

        //===================================

        if (student != null)

        {

            Console.WriteLine($"   Student name is: {student.Name}");

            if (student.Courses != null)

                {

                    Console.WriteLine($"   First enrolled course is: {student.Courses[2]}");

                }

        }   

    }

}

​

public class Student

{

    public string? Name { get; set; }

    public List<string> Courses { get; set; }

​

    public Student(string name, List<string> courses)

    {

        Name = name;

        Courses = courses;

    }

​

    public void Enroll(string course)

    {

        Courses.Add(course);

    }

}