// GET: Instructors
public async Task<ActionResult> Index(int? id, int? courseID)
{
//var instructors = db.Instructors.Include(i => i.OfficeAssignment);
//return View(await instructors.ToListAsync());
var viewModel = new InstructorIndexData();
viewModel.Instructors = db.Instructors
.Include(i => i.OfficeAssignment)
.Include(i => i.Courses.Select(c => c.Department))
.OrderBy(i => i.LastName);
if (id != null)
{
ViewBag.InstructorID = id.Value;
viewModel.Courses = viewModel.Instructors.Where(i =>
i.InstructorID == id.Value).Single().Courses;
}
if (courseID != null)
{
ViewBag.CourseID = courseID.Value;
viewModel.Enrollments = viewModel.Courses.Where(
x => x.CourseID == courseID).Single().Enrollments;
}
return View(viewModel);
}
// GET: Instructor
public ActionResult Index(int? id, int? courseID)
{
var viewModel = new InstructorIndexData();
viewModel.Instructors = db.Instructors
.Include(i => i.OfficeAssignment)
.Include(i => i.Courses.Select(c => c.Department))
.OrderBy(i => i.LastName);
if (id != null)
{
ViewBag.InstructorID = id.Value;
viewModel.Courses = viewModel.Instructors
.Where(i => i.ID == id.Value)
.Single()
.Courses;
}
if (courseID != null)
{
ViewBag.CourseID = courseID.Value;
//Lazy loading
//viewModel.Enrollments = viewModel.Courses.Where(x => x.CourseID == courseID).Single().Enrollments;
//Explicit loading
var selectedCourse = viewModel.Courses.Where(x => x.CourseID == courseID).Single();
db.Entry(selectedCourse).Collection(x => x.Enrollments).Load();
foreach (Enrollment enrollment in selectedCourse.Enrollments)
{
db.Entry(enrollment).Reference(x => x.Student).Load();
}
viewModel.Enrollments = selectedCourse.Enrollments;
}
return View(viewModel);
}
// GET: Instructor
public ActionResult Index(int? id, int? courseID)
{
var viewModel = new InstructorIndexData();
viewModel.Instructors = db.Instructors
.Include(i => i.OfficeAssignment)
.Include(i => i.Courses.Select(c => c.Department))
.OrderBy(i => i.LastName);
if (id != null)
{
ViewBag.InstructorID = id.Value;
viewModel.Courses = viewModel.Instructors
.Single(i => i.ID == id.Value).Courses;
}
if (courseID != null)
{
ViewBag.CourseID = courseID.Value;
viewModel.Enrollments = viewModel.Courses
.Single(x => x.CourseID == courseID).Enrollments;
}
var instructors = db.Instructors.Include(i => i.OfficeAssignment);
return View(viewModel);
}
//
// GET: /Instructor/
public ActionResult Index(int? id, int? courseID)
{
var viewModel = new InstructorIndexData();
viewModel.Instructors = instructorRepository.GetInstructorsWithOfficeAssigmentAndCourses()
.OrderBy(i => i.LastName);
if (id != null)
{
ViewBag.InstructorID = id.Value;
viewModel.Courses = viewModel.Instructors.
Where(i => i.InstructorID == id.Value).Single().Courses;
}
if (courseID != null)
{
ViewBag.CourseID = courseID.Value;
viewModel.Enrollments = viewModel.Courses
.Where(c => c.CourseID == courseID.Value).Single().Enrollments;
}
return View(viewModel);
}
//
// GET: /Instructor/
public ActionResult Index(Int32? id, Int32? courseID)
{
var viewModel = new InstructorIndexData();
viewModel.Instructors = db.Instructors
.Include(i => i.Courses.Select(c => c.Department))
.OrderBy(i => i.LastName);
if (id != null)
{
ViewBag.PersonID = id.Value;
viewModel.Courses = viewModel.Instructors.Where(i => i.PersonID == id.Value).Single().Courses;
}
//if (courseID != null)
//{
// ViewBag.CourseID = courseID.Value;
// viewModel.Enrollments = viewModel.Courses.Where(x => x.CourseID == courseID).Single().Enrollments;
//}
if (courseID != null)
{
ViewBag.CourseID = courseID.Value;
var selectedCourse = viewModel.Courses.Where(x => x.CourseID == courseID).Single();
db.Entry(selectedCourse).Collection(x => x.Enrollments).Load();
foreach (Enrollment enrollment in selectedCourse.Enrollments)
{
db.Entry(enrollment).Reference(x => x.Student).Load();
}
viewModel.Enrollments = selectedCourse.Enrollments;
}
return View(viewModel);
}
//
// GET: /Instructor/
public ActionResult Index(int? id, int? courseID)
{
var viewModel = new InstructorIndexData();
viewModel.Instructors = db.Instructors
.Include(i => i.OfficeAssignment)
.Include(i => i.Courses.Select(c => c.Department)) // loads Courses, and for each Course that is loaded it does eager loading for the Course.Department navigation property.
.OrderBy(i => i.LastName);
/*
* When you retrieved the list of instructors, you specified eager loading for the Courses navigation property and for the Department
* property of each course. Then you put the Courses collection in the view model, and now you're accessing the Enrollments navigation
* property from one entity in that collection. Because you didn't specify eager loading for the Course.Enrollments navigation property,
* the data from that property is appearing in the page as a result of lazy loading.
*/
if (id != null)
{
/*
If an instructor ID was selected, the selected instructor is retrieved from the list of instructors in the view model.
* The view model's Courses property is then loaded with the Course entities from that instructor's Courses navigation property.
*
*/
ViewBag.PersonID = id.Value;
viewModel.Courses = viewModel.Instructors.Where(
i => i.PersonID == id.Value).Single().Courses;
/*
You use the Single method on a collection when you know the collection will have only one item. The Single method throws
* an exception if the collection passed to it is empty or if there's more than one item. An alternative is SingleOrDefault,
* which returns a default value (null in this case) if the collection is empty. However, in this case that would still result
* in an exception (from trying to find a Courses property on a null reference), and the exception message would less clearly
* indicate the cause of the problem.
*/
}
if (courseID != null)
{
ViewBag.CourseID = courseID.Value;
// lazy loading
//viewModel.Enrollments = viewModel.Courses.Where(
// x => x.CourseID == courseID).Single().Enrollments;
// example of explicit loading of the Enrollments property.
var selectedCourse = viewModel.Courses.Where(x => x.CourseID == courseID).Single();
db.Entry(selectedCourse).Collection(x => x.Enrollments).Load(); // explicitly loads that course's Enrollments navigation property:
foreach (Enrollment enrollment in selectedCourse.Enrollments)
{
db.Entry(enrollment).Reference(x => x.Student).Load(); // explicitly loads each Enrollment entity's related Student entity:
}
/* Notice that you use the Collection method to load a collection property, but for a property that holds just one entity, you use the Reference method. */
viewModel.Enrollments = selectedCourse.Enrollments;
}
return View(viewModel);
}
//
// GET: /Instructor/
/// <summary>
/// The method accepts optional query string parameters that provide the ID values of the selected instructor
/// and selected course, and passes all of the required data to the view. The query string parameters are
/// provided by the Select hyperlinks on the page.
/// </summary>
public ActionResult Index(Int32? id, Int32? courseID)
{
var viewModel = new InstructorIndexData();
viewModel.Instructors = db.Instructors
.Include(i => i.Courses.Select(c => c.Department))
.OrderBy(i => i.LastName);
if (id != null)
{
ViewBag.PersonID = id.Value;
viewModel.Courses = viewModel.Instructors.Where(i => i.PersonID == id.Value).Single().Courses;
}
if (courseID != null)
{
ViewBag.CourseID = courseID.Value;
// explicit loading
var selectedCourse = viewModel.Courses.Where(x => x.CourseID == courseID).Single();
db.Entry(selectedCourse).Collection(x => x.Enrollments).Load();
foreach (Enrollment enrollment in selectedCourse.Enrollments)
{
// normally use the Collection method to load a collection property, but
// for a property that holds just one entity, you use the Reference method
db.Entry(enrollment).Reference(x => x.Student).Load();
}
viewModel.Enrollments = selectedCourse.Enrollments;
}
return View(viewModel);
}
