AJAX call to delete DB record - ajax

Question

I have a page that displays a list of courses for an individual. The page allows a user to delete a course from the selected users course list. When the delete button is clicked, that course should be deleted from the course list and the list of courses should be re-displayed. In my controller I was trying to delete the record, then call the listCourses view (view that initially lists the courses for a user) but when I click the delete button, nothing happens. Below is my code:
View to select a student:
#foreach (var stu in Model)
{
<tr>
<td class="stulisttd">
#stu.Id
</td>
<td class="stulisttd">
#stu.fname
</td>
<td class="stulisttd">
#stu.lname
</td>
<td class="thEditButton">
#using (Ajax.BeginForm("addCourses", "ManageStudentCourses", stuEditCourses))
{
#Html.TextBox("stuId", (string)stu.Id, new { #class = "listCourseText" })
<input type="submit" id="addCourses" name="addCourses" value='Add Courses' class="AllTracksButtons" />
}
</td>
<td class="thEditButton">
#using (Ajax.BeginForm("listCourses", "ManageStudentCourses", stuEditCourses))
{
#Html.TextBox("stuId", (string)stu.Id, new { #class = "listCourseText" })
<input type="submit" value="List Courses" class="AllTracksButtons" id=#stu.Id />
}
</td>
</tr>
}
View that lists the courses for user selected:
#foreach (var course in Model)
{
using (Ajax.BeginForm("deleteCourses", "ManageStudentCourses", stuListEditCourses))
{
<tr class="trCourseList">
<td>
#course.courseAbNum
#Html.TextBox("courseAbNum", (string)course.courseAbNum, new { #class = "editCourseText" })
</td>
<td>
#course.courseDesc
</td>
<td>
#course.status
</td>
<td>
#course.grade
</td>
<td>
#course.credits
</td>
<td>
<input type="submit" value="Delete" class="courseListButtons" id="displayEdit" />
</td>
</tr>
}
deleteCourses controller:
public PartialViewResult deleteCourses(string courseAbNum)
{
KuPlanEntities db = new KuPlanEntities();
var deleteCourse = (from course in db.COURSE_TAKEN
where course.courseAbNum == courseAbNum && course.Id == "000160228"
select course);
foreach (var course in deleteCourse)
{
db.COURSE_TAKEN.Remove(course);
db.SaveChanges();
}
var stuCourses = (from studCourse in db.COURSE_TAKEN
join course in db.COURSEs on studCourse.courseAbNum equals course.courseAbNum
where studCourse.Id == "000160228"
select new courseListViewModel { id = studCourse.Id, courseAbNum = studCourse.courseAbNum, status = studCourse.status, grade = studCourse.grade, courseDesc = course.courseDesc, credits = course.credits });
return PartialView("~/Views/ManageStudentCourses/listCourses.cshtml", stuCourses);
}

Answer 1

I think you're going to have an issue with this code
foreach (var course in deleteCourse)
{
db.COURSE_TAKEN.Remove(course);
db.SaveChanges();
}
You'll likely get the error "Collection was modified; enumeration operation may not execute."
To get around this you can use this hack
while (db.COURSE_TAKEN.Where(x => x.ID == ID).Count() != 0)
{
COURSE_TAKEN course = db.COURSE_TAKEN.Where(x => x.ID == ID).FirstOrDefault();
db.COURSE_TAKEN.Remove(course);
db.SaveChanges();
}
Hope this helps.