The relationship could not be changed because one or more of the foreign-key properties is non-nullable

Question

I am getting this error when I GetById   on an entity and then set the collection of child entities to my new list which comes from the MVC view      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    I don t quite understand this line      The relationship could not be changed   because one or more of the foreign-key   properties is non-nullable    Why would I change the relationship between 2 entities  It should remain the same throughout the lifetime of the whole application   The code the exception occurs on is simple assigning modified child classes in a collection to the existing parent class   This would hopefully cater for removal of child classes  addition of new ones and modifications   I would have thought Entity Framework handles this   The lines of code can be distilled to   var thisParent    repo GetById 1   thisParent ChildItems   modifiedParent ChildItems     repo Save

User · Answer

I had same problem  but I knew it had worked OK in other cases  so I reduced the problem to this   parent OtherRelatedItems Clear       this worked OK on SaveChanges   - items were being deleted from DB parent ProblematicItems Clear         this was causing the mentioned exception on SaveChanges      OtherRelatedItems had a composite Primary Key  parentId   some local column  and worked OK ProblematicItems had their own single-column Primary Key  and the parentId was only a FK  This was causing the exception after Clear      All I had to do was to make the ParentId a part of composite PK to indicate that the children can t exist without a parent  I used DB-first model  added the PK and marked the parentId column as EntityKey  so  I had to update it both in DB and EF - not sure if EF alone would be enough       Once you think about it  it s a very elegant distinction that EF uses to decide if children  make sense  without a parent  in this case Clear   won t delete them and throw exception unless you set the ParentId to something else special   or - like in the original question - we expect the items to be deleted once they are removed from the parent

User · Answer

You must manually clear the ChildItems collection and append new items into it    thisParent ChildItems Clear    thisParent ChildItems AddRange modifiedParent ChildItems     After that you can call DeleteOrphans extension method which will handle with orphaned entities  it must be called between DetectChanges and SaveChanges methods     public static class DbContextExtensions       private static readonly ConcurrentDictionary lt  EntityType  ReadOnlyDictionary lt  string  NavigationProperty gt  gt  s navPropMappings   new ConcurrentDictionary lt  EntityType  ReadOnlyDictionary lt  string  NavigationProperty gt  gt          public static void DeleteOrphans  this DbContext source                 var context     IObjectContextAdapter source  ObjectContext          foreach  var entry in context ObjectStateManager GetObjectStateEntries EntityState Modified                         var entityType   entry EntitySet ElementType as EntityType              if  entityType    null                  continue               var navPropMap   s navPropMappings GetOrAdd entityType  CreateNavigationPropertyMap               var props   entry GetModifiedProperties   ToArray                foreach  var prop in props                                NavigationProperty navProp                  if   navPropMap TryGetValue prop  out navProp                       continue                   var related   entry RelationshipManager GetRelatedEnd navProp RelationshipType FullName  navProp ToEndMember Name                   var enumerator   related GetEnumerator                    if  enumerator MoveNext    amp  amp  enumerator Current    null                      continue                   entry Delete                    break                                     private static ReadOnlyDictionary lt string  NavigationProperty gt  CreateNavigationPropertyMap  EntityType type                 var result   type NavigationProperties              Where v   gt  v FromEndMember RelationshipMultiplicity    RelationshipMultiplicity Many               Where v   gt  v ToEndMember RelationshipMultiplicity    RelationshipMultiplicity One     v ToEndMember RelationshipMultiplicity    RelationshipMultiplicity ZeroOrOne  amp  amp  v FromEndMember GetEntityType      v ToEndMember GetEntityType                  Select v   gt  new   NavigationProperty   v  DependentProperties   v GetDependentProperties   Take 2  ToArray                   Where v   gt  v DependentProperties Length    1               ToDictionary v   gt  v DependentProperties 0  Name  v   gt  v NavigationProperty            return new ReadOnlyDictionary lt string  NavigationProperty gt  result

User · Answer

This happens because the Child Entity is marked as Modified instead of Deleted   And the modification that EF does to the Child Entity when parent Remove child  is executed  is simply setting the reference to its parent to null   You can check the child s EntityState by typing the following code into Visual Studio s Immediate Window when the exception occurs  after executing SaveChanges      context ObjectStateManager GetObjectStateEntries System Data EntityState Modified  ElementAt X  Entity   where X should be replaced by the deleted Entity   If you don t have access to the ObjectContext to execute  context ChildEntity Remove child   you can solve this issue by making the foreign key a part of the primary key on the child table   Parent                     PK    IdParent           Name                           Child                     PK    IdChild      PK FK IdParent           Name                            This way  if you execute parent Remove child   EF will correctly mark the Entity as Deleted

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I also solved my problem with Mosh s answer and I thought PeterB s answer was a bit of since it used an enum as foreign key  Remember that you will need to add a new migration after adding this code   I can also recommend this blog post for other solutions   http   www kianryan co uk 2013 03 orphaned-child   Code   public class Child        Key  Column Order   0   DatabaseGenerated DatabaseGeneratedOption Identity       public int Id   get  set         public string Heading   get  set          Add other properties here        Key  Column Order   1       public int ParentId   get  set         public virtual Parent Parent   get  set

User · Answer

I ve tried these solutions and many others  but none of them quite worked out  Since this is the first answer on google  I ll add my solution here   The method that worked well for me was to take relationships out of the picture during commits  so there was nothing for EF to screw up   I did this by re-finding the parent object in the DBContext  and deleting that  Since the re-found object s navigation properties are all null  the childrens  relationships are ignored during the commit   var toDelete   db Parents Find parentObject ID   db Parents Remove toDelete   db SaveChanges      Note that this assumes the foreign keys are setup with ON DELETE CASCADE  so when the parent row is removed  the children will be cleaned up by the database

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This issue arise because we try to delete the parent table still child table data is present  We solve the problem with help of cascade delete   In model Create method in dbcontext class     modelBuilder Entity lt Job gt                     HasMany lt JobSportsMapping gt  C   gt  C JobSportsMappings                   WithRequired C   gt  C Job                   HasForeignKey C   gt  C JobId  WillCascadeOnDelete true               modelBuilder Entity lt Sport gt                     HasMany lt JobSportsMapping gt  C   gt  C JobSportsMappings                     WithRequired C   gt  C Sport                     HasForeignKey C   gt  C SportId  WillCascadeOnDelete true     After that In our API Call  var JobList   Context Job                                   Include x   gt  x JobSportsMappings                                       ToList    Context Job RemoveRange JobList   Context SaveChanges      Cascade delete option delete the parent as well parent related child table with this simple code  Make it try in this simple way   Remove Range which used for delete the list of records in the database Thanks

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If you are using Auto mapper and facing the the issue following is the good solution  it work for me https   www codeproject com Articles 576393 Solutionplusto-aplus-Theplusoperationplusfailed Since the problem is that we re mapping null navigation properties  and we actually don t need them to be updated on the Entity since they didn t changed on the Contract  we need to ignore them on the mapping definition  ForMember dest   gt  dest RefundType  opt   gt  opt Ignore     So my code ended up like this  Mapper CreateMap lt MyDataContract  MyEntity gt  ForMember dest   gt  dest NavigationProperty1  opt   gt  opt Ignore    ForMember dest   gt  dest NavigationProperty2  opt   gt  opt Ignore     IgnoreAllNonExisting

User · Answer

This is a very big problem  What actually happens in your code is this    You load Parent from the database and get an attached entity You replace its child collection with new collection of detached children You save changes but during this operation all children are considered as added becasue EF didn t know about them till this time  So EF tries to set null to foreign key of old children and insert all new children    duplicate rows    Now the solution really depends on what you want to do and how would you like to do it    If you are using ASP NET MVC you can try to use UpdateModel or TryUpdateModel   If you want just update existing children manually  you can simply do something like   foreach  var child in modifiedParent ChildItems        context Childs Attach child        context Entry child  State   EntityState Modified     context SaveChanges      Attaching is actually not needed  setting the state to Modified will also attach the entity  but I like it because it makes the process more obvious   If you want to modify existing  delete existing and insert new childs you must do something like   var parent   context Parents GetById 1      Make sure that childs are loaded as well foreach var child in modifiedParent ChildItems        var attachedChild   FindChild parent  child Id       if  attachedChild    null                   Existing child - apply new values         context Entry attachedChild  CurrentValues SetValues child             else                  New child            Don t insert original object  It will attach whole detached graph         parent ChildItems Add child Clone                 Now you must delete all entities present in parent ChildItems but missing    in modifiedParent ChildItems    ToList should make copy of the collection because we can t modify collection    iterated by foreach foreach var child in parent ChildItems ToList          var detachedChild   FindChild modifiedParent  child Id       if  detachedChild    null                parent ChildItems Remove child           context Childs Remove child             context SaveChanges

User · Answer

I was face same problem when I am going to delete my record than some issue was occur   for this issue solution is that when you are going to delete your record than you missing some thing before deleting header master record you must write to code for delete its detail before header Master I hope you issue will be resolve

User · Answer

I ran into this problem today and wanted to share my solution  In my case  the solution was to delete the Child items before getting the Parent from the database   Previously I was doing it like in the code below  I will then get the same error listed in this question   var Parent   GetParent parentId   var children   Parent Children  foreach  var c in children          Context Children Remove c     Context SaveChanges      What worked for me  is to get the children items first  using the parentId  foreign key  and then delete those items  Then I can get the Parent from the database and at that point  it should not have any children items anymore and I can add new children items   var children   GetChildren parentId   foreach  var c in children          Context Children Remove c     Context SaveChanges     var Parent   GetParent parentId   Parent Children     assign new entities items here

User · Answer

I ve met this problem before several hours and try everything  but in my case the solution was diferent from the listed above   If you use already retrieved entity from the database and try to modify it s childrens the error will occure  but if you get fresh copy of the entity from the database there should not be any problems  Do not use this    public void CheckUsersCount CompanyProduct companyProduct           companyProduct Name    Test        Use this    public void CheckUsersCount Guid companyProductId           CompanyProduct companyProduct   CompanyProductManager Get companyProductId         companyProduct Name    Test

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I ve no idea why the other two answers are so popular    I believe you were right in assuming the ORM framework should handle it - after all  that is what it promises to deliver  Otherwise your domain model gets corrupted by persistence concerns   NHibernate manages this happily if you setup the cascade settings correctly  In  Entity Framework it is also possible  they just expect you to follow better standards when setting up your database model  especially when they have to infer what cascading should be done   You have to define the parent - child relationship correctly by using an  identifying relationship    If you do this  Entity Framework knows the child object is identified by the parent  and therefore it must be a  cascade-delete-orphans  situation   Other than the above  you might need to  from NHibernate experience   thisParent ChildItems Clear    thisParent ChildItems AddRange modifiedParent ChildItems     instead of replacing the list entirely    UPDATE   Slauma s comment reminded me that detached entities are another part of the overall problem  To solve that  you can take the approach of using a custom model binder that constructs your models by attempting to load it from the context  This blog post shows an example of what I mean

User · Answer

If you are using AutoMapper with Entity Framework on the same class  you might hit this problem  For instance if your class is  class A       public ClassB ClassB   get  set        public int ClassBId   get  set       AutoMapper Map lt A  A gt  input  destination     This will try to copy both properties  In this case  ClassBId is non Nullable  Since AutoMapper will copy destination ClassB   input ClassB  this will cause a problem   Set your AutoMapper to Ignore ClassB property    cfg CreateMap lt A  A gt          ForMember m   gt  m ClassB  opt   gt  opt Ignore        We use the ClassBId

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Using the solution of Slauma  I created some generic functions to help update child objects and collections of child objects   All my persistent objects implement this interface       lt summary gt      Base interface for all persisted entries      lt  summary gt  public interface IBase            lt summary gt          The Id          lt  summary gt      int Id   get  set        With this I implemented these two functions in my Repository           lt summary gt          Check if orgEntry is set update it s values  otherwise add it          lt  summary gt           lt param name  set  gt The collection lt  param gt           lt param name  entry  gt The entry lt  param gt           lt param name  orgEntry  gt The original entry found in the database  can be  lt code gt null lt  code gt  is this is a new entry  lt  param gt           lt returns gt The added or updated entry lt  returns gt      public T AddOrUpdateEntry lt T gt  DbSet lt T gt  set  T entry  T orgEntry  where T   class  IBase               if  entry Id    0    orgEntry    null                        entry Id   0              return set Add entry                     else                       Context Entry orgEntry  CurrentValues SetValues entry               return orgEntry                            lt summary gt          check if each entry of the new list was in the orginal list  if found  update it  if not found add it         all entries found in the orignal list that are not in the new list are removed          lt  summary gt           lt typeparam name  T  gt The type of entry lt  typeparam gt           lt param name  set  gt The database set lt  param gt           lt param name  newList  gt The new list lt  param gt           lt param name  orgList  gt The original list lt  param gt      public void AddOrUpdateCollection lt T gt  DbSet lt T gt  set  ICollection lt T gt  newList  ICollection lt T gt  orgList  where T   class  IBase                  attach or update all entries in the new list         foreach  T entry in newList                           Find out if we had the entry already in the list             var orgEntry   orgList SingleOrDefault e   gt  e Id    0  amp  amp  e Id    entry Id                AddOrUpdateEntry set  entry  orgEntry                         Remove all entries from the original list that are no longer in the new list         foreach  T orgEntry in orgList Where e   gt  e Id    0  ToList                          if   newList Any e   gt  e Id    orgEntry Id                                 set Remove orgEntry                                   To use it i do the following   var originalParent    dbContext ParentItems      Where p   gt  p Id    parent Id       Include p   gt  p ChildItems       Include p   gt  p ChildItems2       SingleOrDefault        Add the parent  including collections  to the context or update it s values  except the collections  originalParent   AddOrUpdateEntry  dbContext ParentItems  parent  originalParent       Update each collection AddOrUpdateCollection  dbContext ChildItems  parent ChildItems  orgiginalParent ChildItems   AddOrUpdateCollection  dbContext ChildItems2  parent ChildItems2  orgiginalParent ChildItems2     Hope this helps    EXTRA  You could also make a seperate DbContextExtentions  or your own context inferface  class   public static void DbContextExtentions            lt summary gt          Check if orgEntry is set update it s values  otherwise add it          lt  summary gt           lt param name   dbContext  gt The context object lt  param gt           lt param name  set  gt The collection lt  param gt           lt param name  entry  gt The entry lt  param gt           lt param name  orgEntry  gt The original entry found in the database  can be  lt code gt null lt  code gt  is this is a new entry  lt  param gt           lt returns gt The added or updated entry lt  returns gt      public static T AddOrUpdateEntry lt T gt  this DbContext  dbContext  DbSet lt T gt  set  T entry  T orgEntry  where T   class  IBase               if  entry IsNew    orgEntry    null     New or not found in context                       entry Id   0              return set Add entry                     else                        dbContext Entry orgEntry  CurrentValues SetValues entry               return orgEntry                            lt summary gt          check if each entry of the new list was in the orginal list  if found  update it  if not found add it         all entries found in the orignal list that are not in the new list are removed          lt  summary gt           lt typeparam name  T  gt The type of entry lt  typeparam gt           lt param name   dbContext  gt The context object lt  param gt           lt param name  set  gt The database set lt  param gt           lt param name  newList  gt The new list lt  param gt           lt param name  orgList  gt The original list lt  param gt      public static void AddOrUpdateCollection lt T gt  this DbContext  dbContext  DbSet lt T gt  set  ICollection lt T gt  newList  ICollection lt T gt  orgList  where T   class  IBase                  attach or update all entries in the new list         foreach  T entry in newList                           Find out if we had the entry already in the list             var orgEntry   orgList SingleOrDefault e   gt  e Id    0  amp  amp  e Id    entry Id                AddOrUpdateEntry  dbContext  set  entry  orgEntry                         Remove all entries from the original list that are no longer in the new list         foreach  T orgEntry in orgList Where e   gt  e Id    0  ToList                          if   newList Any e   gt  e Id    orgEntry Id                                 set Remove orgEntry                                     and use it like   var originalParent    dbContext ParentItems      Where p   gt  p Id    parent Id       Include p   gt  p ChildItems       Include p   gt  p ChildItems2       SingleOrDefault        Add the parent  including collections  to the context or update it s values  except the collections  originalParent    dbContext AddOrUpdateEntry  dbContext ParentItems  parent  originalParent       Update each collection  dbContext AddOrUpdateCollection  dbContext ChildItems  parent ChildItems  orgiginalParent ChildItems    dbContext AddOrUpdateCollection  dbContext ChildItems2  parent ChildItems2  orgiginalParent ChildItems2

User · Answer

I just had the same error  I have two tables with a parent child relationship  but I configured a  on delete cascade  on the foreign key column in the table definition of the child table  So when I manually delete the parent row  via SQL  in the database it will automatically delete the child rows   However this did not work in EF  the error described in this thread showed up  The reason for this was  that in my entity data model  edmx file  the properties of the association between the parent and the child table were not correct  The End1 OnDelete option was configured to be none   End1  in my model is the end which has a multiplicity of 1    I manually changed the End1 OnDelete option to Cascade and than it worked  I do not know why EF is not able to pick this up  when I update the model from the database  I have a database first model    For completeness  this is how my code to delete looks like      public void Delete int id                MyType myObject    context MyTypes Find id             context MyTypes Remove myObject            context SaveChanges                If I hadn  t a cascade delete defined  I would have to delete the child rows manually before deleting the parent row

User · Answer

I found this answer much more helpful for the same error  It seems that EF does not like it when you Remove  it prefers Delete   You can delete a collection of records attached to a record like this   order OrderDetails ToList   ForEach s   gt  db Entry s  State   EntityState Deleted     In the example  all of the Detail records attached to an Order have their State set to Delete   In preparation to Add back updated Details  as part of an Order update

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The reason you re facing this is due to the difference between composition and aggregation    In composition  the child object is created when the parent is created and is destroyed when its parent is destroyed  So its lifetime is controlled by its parent  e g  A blog post and its comments  If a post is deleted  its comments should be deleted  It doesn t make sense to have comments for a post that doesn t exist  Same for orders and order items   In aggregation  the child object can exist irrespective of its parent  If the parent is destroyed  the child object can still exist  as it may be added to a different parent later  e g   the relationship between a playlist and the songs in that playlist  If the playlist is deleted  the songs shouldn t be deleted  They may be added to a different playlist   The way Entity Framework differentiates aggregation and composition relationships is as follows    For composition  it expects the child object to a have a composite primary key  ParentID  ChildID   This is by design as the IDs of the children should be within the scope of their parents   For aggregation  it expects the foreign key property in the child object to be nullable    So  the reason you re having this issue is because of how you ve set your primary key in your child table  It should be composite  but it s not  So  Entity Framework sees this association as aggregation  which means  when you remove or clear the child objects  it s not going to delete the child records  It ll simply remove the association and sets the corresponding foreign key column to NULL  so those child records can later be associated with a different parent   Since your column does not allow NULL  you get the exception you mentioned    Solutions   1- If you have a strong reason for not wanting to use a composite key  you need to delete the child objects explicitly  And this can be done simpler than the solutions suggested earlier   context Children RemoveRange parent Children     2- Otherwise  by setting the proper primary key on your child table  your code will look more meaningful   parent Children Clear

User · Answer

You should delete old child items thisParent ChildItems one by one manually  Entity Framework doesn t do that for you  It finally cannot decide what you want to do with the old child items - if you want to throw them away or if you want to keep and assign them to other parent entities  You must tell Entity Framework your decision  But one of these two decisions you HAVE to make since the child entities cannot live alone without a reference to any parent in the database  due to the foreign key constraint   That s basically what the exception says    Edit  What I would do if child items could be added  updated and deleted   public void UpdateEntity ParentItem parent           Load original parent including the child item collection     var originalParent    dbContext ParentItems          Where p   gt  p ID    parent ID           Include p   gt  p ChildItems           SingleOrDefault           We assume that the parent is still in the DB and don t check for null         Update scalar properties of parent         can be omitted if we don t expect changes of the scalar properties     var parentEntry    dbContext Entry originalParent       parentEntry CurrentValues SetValues parent        foreach  var childItem in parent ChildItems                var originalChildItem   originalParent ChildItems              Where c   gt  c ID    childItem ID  amp  amp  c ID    0               SingleOrDefault               Is original child item with same ID in DB          if  originalChildItem    null                           Yes - gt  Update scalar properties of child item             var childEntry    dbContext Entry originalChildItem               childEntry CurrentValues SetValues childItem                     else                          No - gt  It s a new child item - gt  Insert             childItem ID   0              originalParent ChildItems Add childItem                           Don t consider the child items we have just added above          We need to make a copy of the list by using  ToList   because         dbContext ChildItems Remove in this loop does not only delete        from the context but also from the child collection  Without making        the copy we would modify the collection we are just interating        through - which is forbidden and would lead to an exception       foreach  var originalChildItem in                  originalParent ChildItems Where c   gt  c ID    0  ToList                     Are there child items in the DB which are NOT in the            new child item collection anymore          if   parent ChildItems Any c   gt  c ID    originalChildItem ID                  Yes - gt  It s a deleted child item - gt  Delete              dbContext ChildItems Remove originalChildItem               dbContext SaveChanges        Note  This is not tested  It s assuming that the child item collection is of type ICollection   I usually have IList and then the code looks a bit different   I ve also stripped away all repository abstractions to keep it simple   I don t know if that is a good solution  but I believe that some kind of hard work along these lines must be done to take care of all kinds of changes in the navigation collection  I would also be happy to see an easier way of doing it

User · Answer

I used Mosh s solution  but it was not obvious to me how to implement the composition key correctly in code first    So here is the solution   public class Holiday        Key  Column Order   0   DatabaseGenerated DatabaseGeneratedOption Identity       public int HolidayId   get  set         Key  Column Order   1   ForeignKey  Location        public LocationEnum LocationId   get  set         public virtual Location Location   get  set         public DateTime Date   get  set        public string Name   get  set

User · Answer

This type of solution did the trick for me   Parent original   db Parent SingleOrDefault lt Parent gt  t   gt  t ID    updated ID   db Childs RemoveRange original Childs   updated Childs ToList   ForEach c   gt  original Childs Add c    db Entry lt Parent gt  original  CurrentValues SetValues updated     Its important to say that this deletes all the records and insert them again  But for my case  less then 10  it  s ok   I hope it helps

[entity-framework] The relationship could not be changed because one or more of the foreign-key properties is non-nullable

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