ObjectStateManager cannot track multiple objects with the same key
I know many questions like this have already been asked, but I just can't figure out what is wrong. This is my code:
[HttpGet]
public ViewResult Edit(int id)
{
User user = userRepository.GetAll().FirstOrDefault(x => x.ID == id);
return View("Edit", user);
}
[HttpPost]
[ValidateAntiForgeryToken]
public ActionResult Edit(User user)
{
if (ModelState.IsValid)
{
user.Password = HashHelper.GetHash(user.Password);
if (user.ID == 0) // new user
{
User testUser = userRepository.GetAll().FirstOrDefault(x => x.Name.Equals(user.Name));
if (testUser == null)
userRepository.AddEntity(user);
else
{
ModelState.AddModelError("", "Deze gebruikersnaam bestaat al");
return View(user);
}
}
else // edit existing user
{
User tempUser = userRepository.GetAll().First(x => x.ID == user.ID);
if (!user.Name.Equals(tempUser.Name))
{
// naam werd aangepast
int count = userRepository.GetAll().Count(x => x.Name.Equals(user.Name));
if (count > 0)
{
ModelState.AddModelError("", "Deze gebruikersnaam bestaat al");
return View(user);
}
}
userRepository.UpdateEntity(user);
}
userRepository.SaveChanges();
return RedirectToAction("Index");
}
else
{
return View(user);
}
}
UpdateEntity:
public void UpdateEntity(T entity)
{
var entry = context.Entry(entity);
if (entry.State == EntityState.Detached)
context.Set<T>().Attach(entity);
context.Entry<T>(entity).State = EntityState.Modified;
}
This results in an error:
An object with the same key already exists in the ObjectStateManager. The ObjectStateManager cannot track multiple objects with the same key
I do not understand. Why isn't this working and how can I fix it?
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1 answer
there are several problems;
- Don't call
GetAll()
if you want to get a single object, what if you have thousands of objects in your database. Just implement SingleOrDefault in the repository.
Using:
User testUser = userRepository.FirstOrDefault(x => x.Name.Equals(user.Name));
instead:
User testUser = userRepository.GetAll().FirstOrDefault(x => x.Name.Equals(user.Name));
- After retrieving an existing user from the database, simply update that item with the new values instead of trying to keep the one returned from the page;
use
User tempUser = userRepository.GetAll().First(x => x.ID == user.ID);
tempUser.UserName = user.UserName;
....
SaveChanges();
instead of trying to save the user fetched from the page.
- you need to decide the key of your organization; it's a name, it's an identifier, or both.
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