I have a .Net 4.5 MVC 5 database first project that I'm playing around with. There's a data access layer (Entity Framework 6), a business logic layer and the MVC layer.

If I have an object with relationships in the data layer:

namespace DataAccess
{
    public class Course
    {
        public int CourseID { get; set; }
        public string Title { get; set; }

        public ICollection<Lecture> Lectures { get; set; }
        public ICollection<Tutor> Tutors { get; set; }
    }
    public class Lecture
    {
        public int LectureID { get; set; }
        public string Title { get; set; }
        public DateTime Date { get; set; }
        public ICollection<Student> Students { get; set; }
    }
    public class Tutor
    {
        public int TutorID { get; set; }
        public string Name { get; set; }
    }
    public class Student
    {
        public int StudentID { get; set; }
        public string Name { get; set; }
    }
}

And in my business logic layer I have a method that gets courses:

namespace BusinessLogic
{
    public static IEnumerable<Course> GetCourses()
    {
        using (var db = new MyEntities())
        {
            return db.Courses.Include("Lectures").Include("Lectures.Students").Include("Tutors").ToList();
        }
    }
}

And I get the data using my controller like this:

public class HomeController : Controller
{
    public ActionResult Index()
    {
        var courses = BusinessLogic.GetCourses();
        return View(courses);
    }
}

Why is it, when I query my data in the Razor view like this:

var numLectures = courses.Lectures.Count;
var numStudents = courses.Lectures.Students.Count;
var tutorName = courses.Tutors.LastOrDefault().Name;

I get the application error System.ObjectDisposedException: The ObjectContext instance has been disposed and can no longer be used for operations that require a connection.

I know the connection is disposed after the using statement has finished and that .ToList() will let me navigate the courses object, but how do I navigate the objects inside each course (i.e. lectures, students, tutors etc.)?