After creating a complex data model, now it is time to display the data, following the tutorial.
The task is actually a challenging one, as far as the data display is in a way partial – in the “Instructors” view, the instructors are selectable and their courses are displayed. Then the courses are also selectable and the students enlisted are displayed:
Achieving this is actually not a trivial task at all. This is how the Index() method of the InstructorsController.cs looks like:
|
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 |
public async Task Index(int? id, int? courseId) { var viewModel = new InstructorIndexData(); 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) .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; 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(x => x.Student).LoadAsync(); } viewModel.Enrollments = selectedCourse.Enrollments; } return View(viewModel); } |
It “controls” the Index.cshtml view, which is quite complicated as well. The 2 ifs at the end of the code – @if (Model.Courses != null) and @if (Model.Enrollments != null) show whether the “Select” link is clicked or not. Additionally, I liked the way the CSS class is passed for the row as a string. There is something nice in it:
|
1 2 3 4 5 6 7 8 |
@foreach (var item in Model.Instructors) { string selectedRow = ""; if (item.ID == (int?)ViewData["InstructorId"]) { selectedRow = "success"; } <tr class="@selectedRow"> |
For everything else, the GitHub code is here: https://github.com/Vitosh/ASP/tree/master/EFCoreAsp.NetMvcWebApp/ContosoUniversity006
Enjoy it! 🙂