public async Task <IActionResult> Edit(int?id, byte[] rowVersion)
{
if (id == null)
{
return(NotFound());
}
var departmentToUpdate = await _context.Departments.Include(i => i.Administrator).SingleOrDefaultAsync(m => m.DepartmentID == id);
if (departmentToUpdate == null)
{
Department deletedDepartment = new Department();
await TryUpdateModelAsync(deletedDepartment);
ModelState.AddModelError(string.Empty,
"Unable to save changes. The department was deleted by another user.");
ViewData["InstructorID"] = new SelectList(_context.Instructors, "ID", "FullName", deletedDepartment.InstructorID);
return(View(deletedDepartment));
}
_context.Entry(departmentToUpdate).Property("RowVersion").OriginalValue = rowVersion;
if (await TryUpdateModelAsync <Department>(
departmentToUpdate,
"",
s => s.Name, s => s.StartDate, s => s.Budget, s => s.InstructorID))
{
try
{
await _context.SaveChangesAsync();
return(RedirectToAction("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 changes. The department was deleted by another user.");
}
else
{
var databaseValues = (Department)databaseEntry.ToObject();
if (databaseValues.Name != clientValues.Name)
{
ModelState.AddModelError("Name", $"Current value: {databaseValues.Name}");
}
if (databaseValues.Budget != clientValues.Budget)
{
ModelState.AddModelError("Budget", $"Current value: {databaseValues.Budget:c}");
}
if (databaseValues.StartDate != clientValues.StartDate)
{
ModelState.AddModelError("StartDate", $"Current value: {databaseValues.StartDate:d}");
}
if (databaseValues.InstructorID != clientValues.InstructorID)
{
Instructor databaseInstructor = await _context.Instructors.SingleAsync(i => i.ID == databaseValues.InstructorID);
ModelState.AddModelError("InstructorID", $"Current value: {databaseInstructor.FullName}");
}
ModelState.AddModelError(string.Empty, "The record you attempted to edit "
+ "was modified by another user after you got the original value. The "
+ "edit operation was canceled and the current values in the database "
+ "have been displayed. If you still want to edit this record, click "
+ "the Save button again. Otherwise click the Back to List hyperlink.");
departmentToUpdate.RowVersion = (byte[])databaseValues.RowVersion;
ModelState.Remove("RowVersion");
}
}
}
ViewData["InstructorID"] = new SelectList(_context.Instructors, "ID", "FullName", departmentToUpdate.InstructorID);
return(View(departmentToUpdate));
}
public async Task OnGetAsync(int?id, int?courseID)
{
Instructor = new InstructorIndexData();
Instructor.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() 取消显示全部加载，
.OrderBy(i => i.LastName)
.ToListAsync();
/* SELECT[i].[ID], [i].[FirstName], [i].[HireDate], [i].[LastName], [i.OfficeAssignment].[InstructorID], [i.OfficeAssignment].[Location]
* FROM[Instructor] AS[i]
* LEFT JOIN[OfficeAssignment] AS[i.OfficeAssignment] ON[i].[ID] = [i.OfficeAssignment].[InstructorID]
* ORDER BY[i].[LastName], [i].[ID]
*
* 生成一下两个查询，效率感觉很低呀
*
* SELECT[i.CourseAssignments].[CourseID], [i.CourseAssignments].[InstructorID], [c.Course].[CourseID], [c.Course].[Credits], [c.Course].[DepartmentID], [c.Course].[Title]
* FROM[CourseAssignment] AS[i.CourseAssignments]
* I NNER JOIN[Course] AS[c.Course] ON[i.CourseAssignments].[CourseID] = [c.Course].[CourseID]
* INNER JOIN(
* SELECT DISTINCT [i0].[ID], [i0].[LastName]
* FROM [Instructor] AS [i0]
* LEFT JOIN [OfficeAssignment] AS[i.OfficeAssignment0] ON [i0].[ID] = [i.OfficeAssignment0].[InstructorID]
* ) AS[t] ON[i.CourseAssignments].[InstructorID] = [t].[ID]
* ORDER BY[t].[LastName], [t].[ID]
*/
//if (id != null)
//{
// InstructorID = id.Value;
// Instructor instructor = Instructor.Instructors.Where(i => i.ID == id.Value).Single(); //集合仅包含一个选项的时候才能用，空或者多个都会报异常
// Instructor.Courses = instructor.CourseAssignments.Select(s => s.Course);
//}
//if (courseID != null)
//{
// CourseID = courseID.Value;
// Instructor.Enrollments = Instructor.Courses.Where(x => x.CourseID == courseID).Single().Enrollments;
//}
if (id != null)
{
InstructorID = id.Value;
Instructor instructor = Instructor.Instructors.Single(//直接在Single里面调用where条件
i => i.ID == id.Value);
Instructor.Courses = instructor.CourseAssignments.Select(
s => s.Course);
}
//if (courseID != null)
//{
// CourseID = courseID.Value;
// Instructor.Enrollments = Instructor.Courses.Single(
// x => x.CourseID == courseID).Enrollments;
//} 用下列进行显示load加载
if (courseID != null)
{
CourseID = courseID.Value;
var selectedCourse = Instructor.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();
}
Instructor.Enrollments = selectedCourse.Enrollments;
}
}
