public async Task OnGetAsync(int?id, int?courseID)
{
InstructorData = new InstructorIndexData();
InstructorData.Instructors = await _context.Instructors
.Include(i => i.OfficeAssignment)
.Include(i => i.CourseAssignments)
.ThenInclude(i => i.Course)
.ThenInclude(i => i.Department)
//.Include(i=>i.CourseAssignments)
// .ThenInclude(i=>i.Course)
// .ThenInclude(i=>i.Enrollments)
// .ThenInclude(i=>i.Student)
//.AsNoTracking()
//asnotracking is to be commented out because
//navigation properties only be explicitly loaded for the tracked entities
//the commented method uses the eager loading
//we are now using explicit loading
.OrderBy(i => i.LastName)
.ToListAsync();
if (id != null)
{
InstructorID = id.Value;
Instructor instructor = InstructorData.Instructors
//.Single(i => i.ID == id.Value);
.Where(i => i.ID == id.Value).Single();
//single can be used directly in place of line above
InstructorData.Courses = instructor.CourseAssignments
.Select(s => s.Course);
}
if (courseID != null)
{
courseID = courseID.Value;
var selectedCourses = InstructorData.Courses
.Where(x => x.CourseID == courseID).Single();
//the code below is used fro the explicit loading
//i.e. if we rarely want to see enrollments in a course
//we only load the enrollment data if it's requested
await _context.Entry(selectedCourses).Collection
(x => x.Enrollments).LoadAsync();
foreach (Enrollment enrollment in selectedCourses.Enrollments)
{
await _context.Entry(enrollment).Reference(
x => x.Student).LoadAsync();
}
InstructorData.Enrollments = selectedCourses.Enrollments;
//InstructorData.Enrollments = InstructorData.Courses.
// Single(x => x.CourseID == courseID).Enrollments;
}
}
// To protect from overposting attacks, enable the specific properties you want to bind to, for
// more details, see https://aka.ms/RazorPagesCRUD.
public async Task <IActionResult> OnPostAsync(int id)
{
if (!ModelState.IsValid)
{
return(Page());
}
var departmentToUpdate = await _context.Departments
.Include(i => i.Administrator)
.FirstOrDefaultAsync(m => m.DepartmentID == id);
if (departmentToUpdate == null)
{
return(HandleDeletedDepartment());
}
_context.Entry(departmentToUpdate)
.Property("RowVersion").OriginalValue = Department.RowVersion;
if (await TryUpdateModelAsync <Department>(
departmentToUpdate, "Department",
s => s.Name, s => s.StartDate, s => s.Budget, s => s.InstructorID))
{
try
{
await _context.SaveChangesAsync();
return(RedirectToPage("./Index"));
}
catch (DbUpdateConcurrencyException ex)
{
var exceptionEntry = ex.Entries.Single();
var clientValues = (Department)exceptionEntry.Entity;
var databaseEntry = exceptionEntry.GetDatabaseValues();
if (databaseEntry == null)
{
ModelState.AddModelError(string.Empty, "Unable to Save."
+ "The department was deleted by another user.");
return(Page());
}
var dbValues = (Department)databaseEntry.ToObject();
await SetDbErrorMessage(dbValues, clientValues, _context);
//Save the current RowVersion so next postback matches
//unless a new concurrency issue happens
Department.RowVersion = (byte[])dbValues.RowVersion;
//Clear the model error for next postback
ModelState.Remove("Department.RowVersion");
}
}
InstructorNameSL = new SelectList(_context.Instructors,
"ID", "FullName");
return(Page());
}
