ASP NET MVC - Attaching an entity of type MODELNAME failed because another entity of the same type already has the same primary key value

Question

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 lt B gt  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   gt  x aID    id Value  ToList                aViewModel Vendor   db Cs Where x   gt  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

User · Answer

you can use added method like    dbContext Entry modelclassname  State   EntityState Added    but in many case if you want to use more than one model at that time this won t work because entity is already attached to another entity  So  at that time you can use ADDOrUpdate Entity Migration method which simply migrates object from one to another and as a result you wouldn t get any error    dbContext Set lt modelclassname gt    AddOrUpdate yourmodel

User · Answer

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

User · Answer

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 lt YourEntityType gt    ToList     var isAlreadyTracked                       trackedEntries Any trackedItem   gt  trackedItem Entity Id   myEntityToSave Id     If it exists     if  isAlreadyTracked                                myEntityToSave  trackedEntries First trackedItem   gt  trackedItem Entity Id    myEntityToSave Id  Entity                  else     Attach or Modify depending on your needs

User · Answer

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

User · Answer

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

User · Answer

This problem may also be seen during ViewModel to EntityModel mapping  by using AutoMapper  etc   and trying to include context Entry   State and context SaveChanges   such a using block as shown below would solve the problem  Please keep in mind that context SaveChanges   method is used two times instead of using just after if-block as it must be in using block also   public void Save YourEntity entity        if  entity Id    0                context YourEntity Add entity           context SaveChanges              else               using  var context   new YourDbContext                          context Entry entity  State   EntityState Modified              context SaveChanges      Must be in using block                                 Hope this helps

User · Answer

I solve this problem with a  using  block   using  SqlConnection conn   new SqlConnection connectionString                     stuff to do with data base               or if you are using entity framework      using  DataBaseEntity data   new DataBaseEntity             Here is where I get the idea https   social msdn microsoft com Forums sqlserver es-ES b4b350ba-b0d5-464d-8656-8c117d55b2af problema-al-modificar-en-entity-framework forum vcses   is in spanish  look for the second answer

User · Answer

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

User · Answer

Problem SOLVED   Attach method could potentially help somebody but it wouldn t help in this situation as the document was already being tracked while being loaded in Edit GET controller function  Attach would throw exactly the same error   The issue I encounter here was caused by function canUserAccessA   which loads the A entity before updating the state of object a  This was screwing up the tracked entity and it was changing state of a object to Detached   The solution was to amend canUserAccessA   so that the object I was loading wouldn t be tracked  Function AsNoTracking   should be called while querying the context      User - gt  Receipt validation private bool canUserAccessA int aID        int userID   WebSecurity GetUserId User Identity Name       int aFound   db Model AsNoTracking   Where x   gt  x aID    aID  amp  amp  x UserID  userID  Count         return  aFound  gt  0     if aFound  gt  0  then return true  else return false      For some reason I couldnt use  Find aID  with AsNoTracking   but it doesn t really matter as I could achieve the same by changing the query   Hope this will help anybody with similar problem

User · Answer

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   gt  s StudentID    ViewModel StudentID     and updated this object  Everything works now

User · Answer

Interestingly     dbContext Set lt T gt    AddOrUpdate entityToBeUpdatedWithId     Or if you still is not generic    dbContext Set lt UserEntity gt    AddOrUpdate entityToBeUpdatedWithId     seems to solved my problem smoothly

User · Answer

Try this   var local   yourDbContext Set lt YourModel gt                              Local                           FirstOrDefault f   gt  f Id    yourModel Id   if  local    null      yourDbContext Entry local  State   EntityState Detached    yourDbContext Entry applicationModel  State   EntityState Modified

User · Answer

Reasons I ve encountered this error   Did not use  AsNoTracking   when querying for existing entities  Especially when calling a helper function to check permissions  Calling  Include   on a query and then trying to edit the parent  Example  var ent   repo Query lt Ent gt    Include e  gt e Ent2  First       repo Edit e Ent2   repo Edit e   If I m going to edit a nested object  I try to separate these into separate query calls now  If you can t do that  set the child object to null and iterate through lists  detaching objects like this Editing an old entity in a Put web call  The new item is already added to the repo  so modify that one and have it be saved in super Put    Example of what will throw an error  public void Put key  newItem   var old   repo Query lt Entity gt    Where e  gt Id  key  First        repo Edit old   super Put key newItem         Multiple helper functions edit the same entity  Instead of passing the ID as a parameter into each function  pass a reference to the entity  Error solved

User · Answer

Clear all State   dbContextGlobalERP ChangeTracker Entries   Where e    e Entity    null  ToList   ForEach e    e State   EntityState Detached

User · Answer

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 lt int gt  ids                        var item    context Entry myEntity               item State   EntityState Modified              item Collection x   gt  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

User · Answer

Use AsNoTracking   where you are getting your query      var result   dbcontext YourModel AsNoTracking   Where x   gt  x aID    aID  amp  amp  x UserID  userID  Count

User · Answer

In my case   I had wrote really two times an entity of same type     So I delete it and all things work correctly

User · Answer

I encountered this error where    two methods  A  amp  B  in a single controller both used the same instance of an ApplicationDbContext  and method A called method B       private ApplicationDbContext db         api methods     public JsonResult methodA string id           Resource resource   db Resources Find id           db Entry resource  State   EntityState Modified          db SaveChanges            return methodB              public JsonResult methodB string id           Resource resource   db Resources Find id           db Entry resource  State   EntityState Modified          db SaveChanges            return new JsonResult            I changed method B to have a using statement and rely only on the local db2  After       private ApplicationDbContext db             api methods         public JsonResult methodA string id           Resource resource   db Resources Find id           db Entry resource  State   EntityState Modified          db SaveChanges            return methodB              public JsonResult methodB string id           using  var db2   new ApplicationDbContext                          Resource resource   db2 Resources Find id               db2 Entry resource  State   EntityState Modified              db2 SaveChanges                      return new JsonResult

User · Answer

for me the local copy was the source of the problem  this solved it  var local   context Set lt Contact gt    Local FirstOrDefault c   gt  c ContactId    contact ContactId                   if  local    null                                        context Entry local  State   EntityState Detached

User · Answer

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

User · Answer

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  gt  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

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

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