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 can't use Contains with non-primitive values. Do

Where(l => l.Courses.Select(c => c.CourseId).Contains(courseId)

(or the Id field you use).