Question

I’m just starting out with some entity framework exploration, I figured it was time to see what everybody was complaining about. I am running into an issue where the entities don’t seem to be returning any of the object context. I generated the model from a database with three tables which link to one another.

Courses
Instructors
CanTeach

Relationships are as you would expect: a course can relate to multiple CanTeach entities and an instructor can also relate to multiple CanTeach entities. I also added an OData service to my project which also makes use of the same model. So I can run queries like

from a in CanTeach
where a.Instructor.FirstName == "Barry"
select new { Name = a.Instructor.FirstName + " " + a.Instructor.LastName,
   Course = a.Course.Name}

without issue against the OData endpoint using LINQPad. However when I do a simple query like

public Instructor GetInstructorFromID(int ID)
{
    return context.Instructors.Where(i => i.ID == ID).FirstOrDefault();
}

The CanTeach list is empty. I know everything in EF is lazy loaded and it is possible that my context is out of scope by the time I look at the object context, however even trying to get the object context as soon as the query is run results in and empty object context.

What am I doing wrong?

Edit:

In addition to the answer below I found that

return context.Instructors.Include("CanTeach").Where(i => i.ID == ID).FirstOrDefault();

worked for those looking for more of a fluent API.

Answer 1

Look up the word Include

from a in CanTeach.Include("Instructors")
where a.Instructor.FirstName == "Barry"
select new { Name = a.Instructor.FirstName + " " + a.Instructor.LastName,
            Course = a.Course.Name}