EF LINQ include multiple and nested entities

Question

Ok, I have tri-leveled entities with the following hierarchy: Course -> Module -> Chapter

Here was the original EF LINQ statement:

Course course = db.Courses
                .Include(i => i.Modules.Select(s => s.Chapters))
                .Single(x => x.Id == id); 

Now, I want to include another entity called Lab which is associated with a course.

How do I include the Lab entity?

I tried the following but it didn't work:

Course course = db.Courses
                .Include(i => i.Modules.Select(s => s.Chapters) && i.Lab)
                .Single(x => x.Id == id); 

Any ideas on including the 2nd Entity?

Any piece of advise or information would be highly appreciated. Thanks!

Answer 1

Have you tried just adding another Include:

Course course = db.Courses
                .Include(i => i.Modules.Select(s => s.Chapters))
                .Include(i => i.Lab)
                .Single(x => x.Id == id);

Your solution fails because Include doesn't take a boolean operator

Include(i => i.Modules.Select(s => s.Chapters) &&          i.Lab)
                           ^^^                  ^             ^ 
                          list           bool operator    other list

Update To learn more, download LinqPad and look through the samples. I think it is the quickest way to get familiar with Linq and Lambda.

As a start - the difference between Select and Include is that that with a Select you decide what you want to return (aka projection). The Include is a Eager Loading function, that tells Entity Framework that you want it to include data from other tables.

The Include syntax can also be in string. Like this:

           db.Courses
            .Include("Module.Chapter")
            .Include("Lab")
            .Single(x => x.Id == id);

But the samples in LinqPad explains this better.