Question

If I have these 3 classes:

class Student { int id; string name; } class Course { int id; string name; } class Enrolment { int studentId; int courseId; DateTime enrolmentDate; } 

Then using this:

IEnumerable<Course> FindCoursesForStudent(Student student) {     return from enrolment in Enrolments             where enrolment.studentId == student.id            join course in Courses               on enrolment.courseId equals course.id            select course; } 

I can list all the Courses a Student is enrolled on.

But if a student has enrolled for a course more than once, how would I only show the most recent enrolment for each course?

I’m assuming I need to group by Course and filter where enrolmentDate = Max(enrolmentDate) or something similar?

(If this looks familiar, it’s because it’s a follow-on from my previous LINQ question.)

Answer 1

Enumerable<Course> FindCoursesForStudent(Student student) {     return from enrolment in Enrolments             where enrolment.studentId == student.id            && enrolment.enrolmentDate == (from ed in Enrolments             where ed.enrolmentDate == enrolment.enrolmentDate             select ed.enrolmentDate).Max()            join course in Courses               on enrolment.courseId equals course.id            select course; }