c# "this - ASP.NET MVC-Attaching an entity of type 'MODELNAME' failed because another entity of the same type already has the same primary key value





entry" cannot (13)


Interestingly:

_dbContext.Set<T>().AddOrUpdate(entityToBeUpdatedWithId);

Or if you still is not generic:

_dbContext.Set<UserEntity>().AddOrUpdate(entityToBeUpdatedWithId);

seems to solved my problem smoothly.

In a nutshell the exception is thrown during POSTing wrapper model and changing the state of one entry to 'Modified'. Before changing the state, the state is set to 'Detached' but calling Attach() does throw the same error. I'm using EF6.

Please find my code below(model names have been changed to make it easier to read)

Model

// Wrapper classes
        public class AViewModel
        {
            public A a { get; set; }
            public List<B> b { get; set; }
            public C c { get; set; }
        }   

Controller

        public ActionResult Edit(int? id)
        {
            if (id == null)
            {
                return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
            }

            if (!canUserAccessA(id.Value))
                return new HttpStatusCodeResult(HttpStatusCode.Forbidden);

            var aViewModel = new AViewModel();
            aViewModel.A = db.As.Find(id);

            if (aViewModel.Receipt == null)
            {
                return HttpNotFound();
            }

            aViewModel.b = db.Bs.Where(x => x.aID == id.Value).ToList();
            aViewModel.Vendor = db.Cs.Where(x => x.cID == aViewModel.a.cID).FirstOrDefault();

            return View(aViewModel);
        }

[HttpPost]
        [ValidateAntiForgeryToken]
        public ActionResult Edit(AViewModel aViewModel)
        {
            if (!canUserAccessA(aViewModel.a.aID) || aViewModel.a.UserID != WebSecurity.GetUserId(User.Identity.Name))
                return new HttpStatusCodeResult(HttpStatusCode.Forbidden);

            if (ModelState.IsValid)
            {
                db.Entry(aViewModel.a).State = EntityState.Modified; //THIS IS WHERE THE ERROR IS BEING THROWN
                db.SaveChanges();
                return RedirectToAction("Index");
            }
            return View(aViewModel);
        }

As shown above line

db.Entry(aViewModel.a).State = EntityState.Modified;

throws exception:

Attaching an entity of type 'A' failed because another entity of the same type already has the same primary key value. This can happen when using the 'Attach' method or setting the state of an entity to 'Unchanged' or 'Modified' if any entities in the graph have conflicting key values. This may be because some entities are new and have not yet received database-generated key values. In this case use the 'Add' method or the 'Added' entity state to track the graph and then set the state of non-new entities to 'Unchanged' or 'Modified' as appropriate.

Does anybody see anything wrong in my code or understand in what circumstances it would throw such error during editing a model?




It seems that entity you are trying to modify is not being tracked correctly and therefore is not recognized as edited, but added instead.

Instead of directly setting state, try to do the following:

//db.Entry(aViewModel.a).State = EntityState.Modified;
db.As.Attach(aViewModel.a); 
db.SaveChanges();

Also, I would like to warn you that your code contains potential security vulnerability. If you are using entity directly in your view model, then you risk that somebody could modify contents of entity by adding correctly named fields in submitted form. For example, if user added input box with name "A.FirstName" and the entity contained such field, then the value would be bound to viewmodel and saved to database even if the user would not be allowed to change that in normal operation of application.

Update:

To get over security vulnerability mentioned previously, you should never expose your domain model as your viewmodel but use separate viewmodel instead. Then your action would receive viewmodel which you could map back to domain model using some mapping tool like AutoMapper. This would keep you safe from user modifying sensitive data.

Here is extended explanation:

http://www.stevefenton.co.uk/Content/Blog/Date/201303/Blog/Why-You-Never-Expose-Your-Domain-Model-As-Your-MVC-Model/




Here what I did in the similar case.

That sitatuation means that same entity has already been existed in the context.So following can help

First check from ChangeTracker if the entity is in the context

var trackedEntries=GetContext().ChangeTracker.Entries<YourEntityType>().ToList();

var isAlreadyTracked =
                    trackedEntries.Any(trackedItem => trackedItem.Entity.Id ==myEntityToSave.Id);

If it exists

  if (isAlreadyTracked)
            {
                myEntityToSave= trackedEntries.First(trackedItem => trackedItem.Entity.Id == myEntityToSave.Id).Entity;
            } 

else
{
//Attach or Modify depending on your needs
}



I thought I'd share my experience on this one, even though I feel a bit silly for not realising sooner.

I am using the repository pattern with the repo instances injected into my controllers. The concrete repositories instantiate my ModelContext (DbContext) which lasts the lifetime of the repository, which is IDisposable and disposed by the controller.

The issue for me was that I have a modified stamp and row version on my entities, so I was getting them first in order to compare with the inbound headers. Of course, this loaded and tracked the entity that was subsequently being updated.

The fix was simply to change the repository from newing-up a context once in the constructor to having the following methods:

    private DbContext GetDbContext()
    {
        return this.GetDbContext(false);
    }


    protected virtual DbContext GetDbContext(bool canUseCachedContext)
    {
        if (_dbContext != null)
        {
            if (canUseCachedContext)
            {
                return _dbContext;
            }
            else
            {
                _dbContext.Dispose();
            }
        }

        _dbContext = new ModelContext();

        return _dbContext;
    }

    #region IDisposable Members

    public void Dispose()
    {
        this.Dispose(true);
    }

    protected virtual void Dispose(bool isDisposing)
    {
        if (!_isDisposed)
        {
            if (isDisposing)
            {
                // Clear down managed resources.

                if (_dbContext != null)
                    _dbContext.Dispose();
            }

            _isDisposed = true;
        }
    }

    #endregion

This allows the repository methods to re-new their context instance upon each use by calling GetDbContext, or use a previous instance if they so desire by specifying true.




i mange to fix the issue by updating state. when you trigger find or any other query operation on the same record sate has been updated with modified so we need to set status to Detached then you can fire your update change

     ActivityEntity activity = new ActivityEntity();
      activity.name="vv";
    activity.ID = 22 ; //sample id
   var savedActivity = context.Activities.Find(22);

            if (savedActivity!=null)
            {
                context.Entry(savedActivity).State = EntityState.Detached;
                context.SaveChanges();

                activity.age= savedActivity.age;
                activity.marks= savedActivity.marks; 

                context.Entry(activity).State = EntityState.Modified;
                context.SaveChanges();
                return activity.ID;
            }



I had a similar issue, after probing for 2-3 days found ".AsNoTracking" should be removed as EF doesn't track the changes and assumes there are no changes unless an object is attached. Also if we don't use .AsNoTracking, EF automatically knows which object to save/update so there is no need to use Attach/Added.




Similar to what Luke Puplett is saying, the problem can be caused by not properly disposing or creating your context.

In my case, I had a class which accepted a context called ContextService:

public class ContextService : IDisposable
{
    private Context _context;

    public void Dispose()
    {
        _context.Dispose();
    }
    public ContextService(Context context)
    {
        _context = context;
    }
//... do stuff with the context

My context service had a function which updates an entity using an instantiated entity object:

        public void UpdateEntity(MyEntity myEntity, ICollection<int> ids)
        {
            var item = _context.Entry(myEntity);
            item.State = EntityState.Modified;
            item.Collection(x => x.RelatedEntities).Load();
            myEntity.RelatedEntities.Clear();
            foreach (var id in ids)
            {
                myEntity.RelatedEntities.Add(_context.RelatedEntities.Find(id));
            }
            _context.SaveChanges();
        }

All of this was fine, my controller where I initialized the service was the problem. My controller originally looked like this:

    private static NotificationService _service = 
        new NotificationService(new NotificationContext());
    public void Dispose()
    {
    }

I changed it to this and the error went away:

    private static NotificationService _service;
    public TemplateController()
    {
        _service = new NotificationService(new NotificationContext());
    }
    public void Dispose()
    {
        _service.Dispose();
    }



I had this problem with local var and i just detach it like this:

if (ModelState.IsValid)
{
    var old = db.Channel.Find(channel.Id);
    if (Request.Files.Count > 0)
    {
        HttpPostedFileBase objFiles = Request.Files[0];
        using (var binaryReader = new BinaryReader(objFiles.InputStream))
        {
            channel.GateImage = binaryReader.ReadBytes(objFiles.ContentLength);
        }

    }
    else
        channel.GateImage = old.GateImage;
    var cat = db.Category.Find(CatID);
    if (cat != null)
        channel.Category = cat;
    db.Entry(old).State = EntityState.Detached; // just added this line
    db.Entry(channel).State = EntityState.Modified;
    await db.SaveChangesAsync();
    return RedirectToAction("Index");
}
return View(channel);

Problem causes of loaded objects with same Key, so first we will detach that object and do the the updating to avoid conflict between two object with the same Key




for me the local copy was the source of the problem. this solved it

var local = context.Set<Contact>().Local.FirstOrDefault(c => c.ContactId == contact.ContactId);
                if (local != null)
                {
                    context.Entry(local).State = EntityState.Detached;
                }



Try this:

var local = yourDbContext.Set<YourModel>()
                         .Local
                         .FirstOrDefault(f => f.Id == yourModel.Id);
if (local != null)
{
  yourDbContext.Entry(local).State = EntityState.Detached;
}
yourDbContext.Entry(applicationModel).State = EntityState.Modified;



My case was that I did not have direct access to EF context from my MVC app.

So if you are using some kind of repository for entity persistence it could be appropiate to simply detach explicitly loaded entity and then set binded EntityState to Modified.

Sample (abstract) code:

MVC

public ActionResult(A a)
{
  A aa = repo.Find(...);
  // some logic
  repo.Detach(aa);
  repo.Update(a);
}

Repository

void Update(A a)
{
   context.Entry(a).EntityState = EntityState.Modified;
   context.SaveChanges();
}

void Detach(A a)
{
   context.Entry(a).EntityState = EntityState.Detached;
}



I have added this answer only because the problem is explained based on more complex data pattern and I found it hard to understand here.

I created a fairly simple application. This error occurred inside Edit POST action. The action accepted ViewModel as an input parameter. The reason for using the ViewModel was to make some calculation before the record was saved.

Once the action passed through validation such as if(ModelState.IsValid), my wrongdoing was to project values from ViewModel into a completely new instance of Entity. I thought I'd have to create a new instance to store updated data and then saved such instance.

What I had realised later was that I had to read the record from database:

Student student = db.Students.Find(s => s.StudentID == ViewModel.StudentID);

and updated this object. Everything works now.




Here is another method, You can define a function and pass it 2 values, one the actual number and the second is the max length to fix. i.e.

public string FixZero(string str, int maxlength)
{
    string zero = "000000000000000000000000000000000000000";
    int length = str.Length;
    int diff = maxlength- length;
    string z = zero.Substring(1, diff);
    z = z + str;
    return z;
}

you need integers in the format 0012, FixZero("12", 4) or for 0001234, FixZero("1234", 7)





c# asp.net-mvc entity-framework