public async Task <IActionResult> Index(int?id, int?courseId)
{
var viewModel = new InstructorIndex();
viewModel.Instructors = await _context.Instructors
.Include(i => i.OfficeAssignment)
// These 4 lines are unncessary when using Explicit Loading (below)
//.Include(i => i.CourseAssignments)
//.ThenInclude(i => i.Course)
// .ThenInclude(i => i.Enrollments)
// .ThenInclude(i => i.Student)
.Include(i => i.CourseAssignments)
.ThenInclude(i => i.Course)
.ThenInclude(i => i.Department)
//.AsNoTracking() // Use AsNoTracking with Eager Loading, not with Explicit Loading (below)
.OrderBy(i => i.LastName)
.ToListAsync();
if (id != null)
{
ViewData["Id"] = id.Value;
Instructor instructor = viewModel.Instructors.Where(
i => i.Id == id.Value).Single();
viewModel.Courses = instructor.CourseAssignments.Select(s => s.Course);
}
// Eager Loading or Explicit Loading (below)
//if (courseId != null)
//{
// ViewData["CourseId"] = courseId.Value;
// viewModel.Enrollments = viewModel.Courses.Where(
// x => x.Id == courseId).Single()
// .Enrollments;
//}
// Explicit Loading instead of Eager Loading (above)
if (courseId != null)
{
ViewData["CourseId"] = courseId.Value;
var selectedCourse = viewModel.Courses.Where(x => x.Id == courseId).Single();
await _context.Entry(selectedCourse).Collection(x => x.Enrollments).LoadAsync();
foreach (Enrollment enrollment in selectedCourse.Enrollments)
{
await _context.Entry(enrollment).Reference(x => x.Student).LoadAsync();
}
viewModel.Enrollments = selectedCourse.Enrollments;
}
return(View(viewModel));
}
// GET: Instructors
public async Task <IActionResult> Index(int?id, int?courseId)
{
var viewModel = new InstructorIndex();
viewModel.Instructors = await _context.Instructors
.Include(i => i.OfficeAssignment)
.Include(i => i.CourseAssignments)
//.ThenInclude(i => i.Course)
// .ThenInclude(i => i.Enrollments)
// .ThenInclude(i => i.Student)
.Include(i => i.CourseAssignments)
.ThenInclude(i => i.Course)
.ThenInclude(i => i.Department)
//.AsNoTracking()
.OrderBy(i => i.LastName)
.ToListAsync();
if (id != null)
{
ViewData["InstructorID"] = id.Value;
Instructor instructor = viewModel.Instructors.Where
(i => i.ID == id.Value).Single();
viewModel.Courses = instructor.CourseAssignments.Select(s => s.Course);
}
if (courseId != null)
{
ViewData["CourseID"] = courseId.Value;
//viewModel.Enrollments = viewModel.Courses.Where // based on the courseID being passed into the Index() method returns a list of IEnumerable<Enrollment>
// (x => x.CourseID == courseId).Single().Enrollments; // return a single course with Enrollments
var selectedCourse = viewModel
.Courses
.Where(x => x.CourseID == courseId)
.Single();
await _context.Entry(selectedCourse).Collection(x => x.Enrollments).LoadAsync();
foreach (Enrollment enrollment in selectedCourse.Enrollments)
{
await _context.Entry(enrollment).Reference(s => s.Student).LoadAsync();
}
viewModel.Enrollments = selectedCourse.Enrollments;
}
return(View(viewModel));
}
