LINQ, Unable to create a constant value of type XXX. Only primitive types or enumeration types are supported in this context

Question

In my application I have Lecturers and they have list of Courses they can teach and when I\'m deleting a course I want to remove connection to lecturers. Here\'s the code:

Answer 1

You cannot compare complex type, if you have not specified what you mean for equality.

As exception detail says, you need to check primitive values (like Integer in your case).

And better to use Any() method instead.

var toRemove = db.Lecturers
     .Where(l => l.Courses.Any(p=>p.Id == courseFromDb.Id)).ToList();