I have the following test case
[TestMethod()]
[DeploymentItem("Courses.sdf")]
public void RemoveCourseConfirmedTest()
{
CoursesController_Accessor target = new CoursesController_Accessor();
int id = 50;
ActionResult actual;
CoursesDBContext db = target.db;
Course courseToDelete = db.Courses.Find(id);
List<CourseMeet> meets = courseToDelete.meets.ToList<CourseMeet>();
actual = target.RemoveCourseConfirmed(courseToDelete);
foreach (var meet in meets)
{
Assert.IsNull(db.Meets.find(meet));
}
Assert.IsNull(db.Courses.Find(courseToDelete.courseID));
}
Which tests the following method from my controller.
[HttpPost, ActionName("RemoveCourse")]
public ActionResult RemoveCourseConfirmed(Course course)
{
try
{
db.Entry(course).State = EntityState.Deleted;
db.SaveChanges();
return RedirectToAction("Index");
}
catch (DbUpdateConcurrencyException)
{
return RedirectToAction("RemoveMeet", new System.Web.Routing.RouteValueDictionary { { "concurrencyError", true } });
}
catch (DataException)
{
ModelState.AddModelError(string.Empty, "Unable to save changes. Try again.");
return View(course);
}
}
I know i should be using a Mock db .... but for this project I have decided to go with this approach.
So this what happens. When I run the actual web site this function works perfectly fine and removes the course and all the meets that belong to it.
But when I run the test i get the following exception
System.InvalidOperationException: The operation failed: The relationship could not be
changed because one or more of the foreign-key properties is non-nullable. When a change is
made to a relationship, the related foreign-key property is set to a null value. If the
foreign-key does not support null values, a new relationship must be defined, the foreign-
key property must be assigned another non-null value, or the unrelated object must be
deleted.
Here is the even more interesting part if I comment out the following line from the test
List<CourseMeet> meets = courseToDelete.meets.ToList<CourseMeet>();
and replace the loop with the following:
foreach (var meet in db.Meets.ToList())
{
Assert.IsFalse(meet.courseID == courseToDelete.courseID);
}
I dont get any exceptions and the test case passess.
Am I missing something about Entity Framework or is this a bug?
Well this has been open for a while now. I still haven't been able to find a definite answer but working more with MVC and EF i think what is happening is that once i execute the line
List<CourseMeet> meets = courseToDelete.meets.ToList<CourseMeet>();
the meets get loaded into the object manager and hence when the parent object is deleted the no longer have a reference to the parent course.