using System;

using System.Linq;

using System.Collections.Generic;

public class Student

{

    public string StudentName { get; set; }

    public string StudentEmail { get; set; }

}

​

public class Enrolled

{

    public Student Student { get; set; }

    public string Subject { get; set; }

}

​

public class Dropped

{

    public Student Student { get; set; }

    public string Subject { get; set; }

}

​

​

​

public class Program

{

    public static void Main()

    {

        // Populating the List.

// Setup the Student List

List<Student> lstStudents = new List<Student>();

​

var John = new Student()

{

    StudentEmail = "john@stanford.edu",

    StudentName = "John Wayne"

};

​

var Maya = new Student()

{

    StudentEmail = "maya@stanford.edu",

    StudentName = "Maya Agnes"

};

​

var Eric = new Student()

{

    StudentEmail = "eric@stanford.edu",

    StudentName = "Eric James"

};

​

var Ellen = new Student()

{

    StudentEmail = "ellen@stanford.edu",

    StudentName = "Ellen Page"

};

​

lstStudents.Add(John);

lstStudents.Add(Maya);

lstStudents.Add(Eric);

lstStudents.Add(Ellen);

​

// Setup the Enrolled List

List<Enrolled> lstEnrolled = new List<Enrolled>();

​

// John

var JohnMath = new Enrolled() { Student = John, Subject = "Math" };

var JohnScience = new Enrolled() { Student = John, Subject = "Science" };

var JohnEnglish = new Enrolled() { Student = John, Subject = "English" };

​

// Maya

var MayaMath = new Enrolled() { Student = Maya, Subject = "Math" };

​

// Eric

var EricMath = new Enrolled() { Student = Eric, Subject = "Math" };

var EricScience = new Enrolled() { Student = Eric, Subject = "Science" };

var EricSocial = new Enrolled() { Student = Eric, Subject = "Social" };

​

// Ellen

var EllenMath = new Enrolled() { Student = Ellen, Subject = "Math" };

var EllenScience = new Enrolled() { Student = Ellen, Subject = "Science" };

var EllenEnglish = new Enrolled() { Student = Ellen, Subject = "English" };

var EllenSocial = new Enrolled() { Student = Ellen, Subject = "Social" };

​

lstEnrolled.Add(JohnMath);

lstEnrolled.Add(JohnScience);

lstEnrolled.Add(JohnEnglish);

lstEnrolled.Add(MayaMath);

lstEnrolled.Add(EricMath);

lstEnrolled.Add(EricScience);

lstEnrolled.Add(EricSocial);

lstEnrolled.Add(EllenMath);

lstEnrolled.Add(EllenScience);

lstEnrolled.Add(EllenEnglish);

lstEnrolled.Add(EllenSocial);

​

// Setup the Dropped List

List<Dropped> lstDropped = new List<Dropped>();

​

// John dropped Math

var JohnDropMath = new Dropped() { Student = John, Subject = "Math" };

​

// Eric dropped Social

var EricDropSocial = new Dropped() { Student = Eric, Subject = "Social" };

​

// Ellen Dropped Math

var EllenDropMath = new Dropped() { Student = Ellen, Subject = "Math" };

​

lstDropped.Add(JohnDropMath);

lstDropped.Add(EricDropSocial);

lstDropped.Add(EllenDropMath);

var result = lstEnrolled.Where(e => !lstDropped.Any(d => d.Student == e.Student && d.Subject == e.Subject))  //omit dropped courses

     .GroupBy(x => x.Student) // group results by students

     .Select(x => new {

            Name = x.First().Student.StudentName.Split(' ').First(), 

            Subjects = string.Join(", ", x.Select(e => e.Subject)) 

       }).ToArray();

foreach(var x in result)

Console.WriteLine($"{x.Name}\t{x.Subjects}");

}

}