How to add update child entities when updating a parent entity in EF

Question

The two entities are one-to-many relationship  built by code first fluent api    public class Parent       public Parent                 this Children   new List lt Child gt                public int Id   get  set         public virtual ICollection lt Child gt  Children   get  set       public class Child       public int Id   get  set         public int ParentId   get  set         public string Data   get  set        In my WebApi controller I have actions to create a parent entity which is working fine  and update a parent entity which has some problem   The update action looks like   public void Update UpdateParentModel model          what should be done here      Currently I have two ideas    Get a tracked parent entity named existing by model Id  and assign values in model one by one to the entity  This sounds stupid  And in model Children I don t know which child is new  which child is modified or even deleted   Create a new parent entity via model  and attached it to the DbContext and save it  But how can the DbContext know the state of children  new add delete modified     What s the correct way of implement this feature

User · Answer

var parent   context Parent FirstOrDefault x   gt  x Id    modelParent Id   if  parent    null      parent Childs   modelParent Childs      source

User · Answer

Because the model that gets posted to the WebApi controller is detached from any entity-framework  EF  context  the only option is to load the object graph  parent including its children  from the database and compare which children have been added  deleted or updated   Unless you would track the changes with your own tracking mechanism during the detached state  in the browser or wherever  which in my opinion is more complex than the following   It could look like this  public void Update UpdateParentModel model        var existingParent    dbContext Parents          Where p   gt  p Id    model Id           Include p   gt  p Children           SingleOrDefault         if  existingParent    null                   Update parent          dbContext Entry existingParent  CurrentValues SetValues model               Delete children         foreach  var existingChild in existingParent Children ToList                          if   model Children Any c   gt  c Id    existingChild Id                    dbContext Children Remove existingChild                         Update and Insert children         foreach  var childModel in model Children                        var existingChild   existingParent Children                  Where c   gt  c Id    childModel Id  amp  amp  c Id    default int                    SingleOrDefault                 if  existingChild    null                     Update child                  dbContext Entry existingChild  CurrentValues SetValues childModel               else                                  Insert child                 var newChild   new Child                                       Data   childModel Data                                                               existingParent Children Add newChild                                     dbContext SaveChanges                CurrentValues SetValues can take any object and maps property values to the attached entity based on the property name  If the property names in your model are different from the names in the entity you can t use this method and must assign the values one by one

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There are a few projects out there that make the interaction between the client and the server easier as far as it concerns saving an entire object graph   Here are two you d want to look at    Trackable Entities Breeze    Both the projects above take recognize the disconnected entities when it s returned to the server  detect and save the changes  and return to the client affected data

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For VB NET developers Use this generic sub to mark the child state  easy to use     Notes          PromatCon  the entity object   amList  is the child list that you want to add or modify   rList  is the child list that you want to remove      updatechild objCas ECC Decision  PromatCon ECC Decision Where Function c  c rid   objCas rid And Not objCas ECC Decision Select Function x  x dcid  Contains c dcid   toList    Sub updatechild Of Ety  amList As ICollection Of Ety   rList As ICollection Of Ety           If amList IsNot Nothing Then             For Each obj In amList                 Dim x   PromatCon Entry obj  GetDatabaseValues                   If x Is Nothing Then                     PromatCon Entry obj  State   EntityState Added                 Else                     PromatCon Entry obj  State   EntityState Modified                 End If             Next         End If          If rList IsNot Nothing Then             For Each obj In rList ToList                 PromatCon Entry obj  State   EntityState Deleted             Next         End If End Sub   PromatCon SaveChanges

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Refer below code snippet from one of my projects where I implemented the same thing  It will make save data if new entry  updates if existing and delete if record is not available in the posting json  Json Data to help you understand the schema         quot groupId quot   1       quot groupName quot    quot Group 1 quot        quot sortOrder quot   1       quot filterNames quot                            quot filterId quot   1               quot filterName1 quot    quot Name11111 quot                quot sortOrder quot   10               quot groupId quot   1                                                quot filterId quot   1006               quot filterName1 quot    quot Name Changed 1 quot                quot sortOrder quot   10               quot groupId quot   1                                                quot filterId quot   1007               quot filterName1 quot    quot New Filter 1 quot                quot sortOrder quot   10               quot groupId quot   1                                               quot filterId quot   2               quot filterName1 quot    quot Name 2 Changed quot                quot sortOrder quot   10               quot groupId quot   1                                                 public async Task lt int gt  UpdateFilter FilterGroup filterGroup                                                var Ids   from f in filterGroup FilterNames select f FilterId              var toBeDeleted   dbContext FilterNames Where x   gt  x GroupId    filterGroup GroupId              amp  amp   Ids Contains x FilterId   ToList                foreach var item in toBeDeleted                                dbContext FilterNames Remove item                             await dbContext SaveChangesAsync                 dbContext FilterGroups Attach filterGroup               dbContext Entry filterGroup  State   EntityState Modified              for int i 0 i lt filterGroup FilterNames Count   i                                              if  filterGroup FilterNames ElementAt i  FilterId    0                                        dbContext Entry filterGroup FilterNames ElementAt i   State   EntityState Modified                                                          return await dbContext SaveChangesAsync

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public async Task lt IHttpActionResult gt  PutParent int id  Parent parent                        if   ModelState IsValid                                return BadRequest ModelState                              if  id    parent Id                                return BadRequest                               db Entry parent  State   EntityState Modified               foreach  Child child in parent Children                                db Entry child  State   child Id    0   EntityState Added   EntityState Modified                             try                               await db SaveChangesAsync                              catch  DbUpdateConcurrencyException                                if   ParentExists id                                         return NotFound                                      else                                       throw                                               return Ok db Parents Find id                This is how I solved this problem  This way  EF knows which to add which to update

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If you are using EntityFrameworkCore you can do the following in your controller post action  The Attach method recursively attaches navigation properties including collections     context Attach modelPostedToController    IEnumerable lt EntityEntry gt  unchangedEntities    context ChangeTracker Entries   Where x   gt  x State    EntityState Unchanged    foreach EntityEntry ee in unchangedEntities        ee State   EntityState Modified     await  context SaveChangesAsync      It is assumed that each entity that was updated has all properties set and provided in the post data from the client  eg  won t work for partial update of an entity    You also need to make sure that you are using a new dedicated entity framework database context for this operation

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I ve been messing about with something like this      protected void UpdateChildCollection lt Tparent  Tid   Tchild gt  Tparent dbItem  Tparent newItem  Func lt Tparent  IEnumerable lt Tchild gt  gt  selector  Func lt Tchild  Tid gt  idSelector  where Tchild   class               var dbItems   selector dbItem  ToList            var newItems   selector newItem  ToList             if  dbItems    null  amp  amp  newItems    null              return           var original   dbItems  ToDictionary idSelector     new Dictionary lt Tid  Tchild gt             var updated   newItems  ToDictionary idSelector     new Dictionary lt Tid  Tchild gt              var toRemove   original Where i   gt   updated ContainsKey i Key   ToArray            var removed   toRemove Select i   gt  DbContext Entry i Value  State   EntityState Deleted  ToArray             var toUpdate   original Where i   gt  updated ContainsKey i Key   ToList            toUpdate ForEach i   gt  DbContext Entry i Value  CurrentValues SetValues updated i Key              var toAdd   updated Where i   gt   original ContainsKey i Key   ToList            toAdd ForEach i   gt  DbContext Set lt Tchild gt    Add i Value            which you can call with something like   UpdateChildCollection dbCopy  detached  p   gt  p MyCollectionProp  collectionItem   gt  collectionItem Id    Unfortunately  this kinda falls over if there are collection properties on the child type which also need to be updated  Considering trying to solve this by passing an IRepository   with basic CRUD methods  which would be responsible for calling UpdateChildCollection on its own   Would call the repo instead of direct calls to DbContext Entry   Have no idea how this will all perform at scale  but not sure what else to do with this problem

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Because I hate repeating complex logic  here s a generic version of Slauma s solution  Here s my update method  Note that in a detached scenario  sometimes your code will read data and then update it  so it s not always detached  public async Task UpdateAsync TempOrder order        order CheckNotNull nameof order        order OrderId CheckNotNull nameof order OrderId         order DateModified    dateService UtcNow       if   context Entry order  State    EntityState Modified                await  context SaveChangesAsync   ConfigureAwait false             else    Detached                var existing   await SelectAsync order OrderId  Value  ConfigureAwait false           if  existing    null                        order DateModified    dateService UtcNow               context TrackChildChanges order Products  existing Products   a  b    gt  a OrderProductId    b OrderProductId               await  context SaveChangesAsync order  existing  ConfigureAwait false                      CheckNotNull is defined here  Create these extension methods       lt summary gt      Tracks changes on childs models by comparing with latest database state       lt  summary gt       lt typeparam name  quot T quot  gt The type of model to track  lt  typeparam gt       lt param name  quot context quot  gt The database context tracking changes  lt  param gt       lt param name  quot childs quot  gt The childs to update  detached from the context  lt  param gt       lt param name  quot existingChilds quot  gt The latest existing data  attached to the context  lt  param gt       lt param name  quot match quot  gt A function to match models by their primary key s   lt  param gt  public static void TrackChildChanges lt T gt  this DbContext context  IList lt T gt  childs  IList lt T gt  existingChilds  Func lt T  T  bool gt  match      where T   class       context CheckNotNull nameof context        childs CheckNotNull nameof childs        existingChilds CheckNotNull nameof existingChilds            Delete childs      foreach  var existing in existingChilds ToList                  if   childs Any c   gt  match c  existing                          existingChilds Remove existing                           Update and Insert childs      var existingChildsCopy   existingChilds ToList        foreach  var item in childs ToList                  var existing   existingChildsCopy              Where c   gt  match c  item                SingleOrDefault             if  existing    null                           Update child              context Entry existing  CurrentValues SetValues item                     else                          Insert child              existingChilds Add item                  context Entry item  State   EntityState Added                          lt summary gt      Saves changes to a detached model by comparing it with the latest data       lt  summary gt       lt typeparam name  quot T quot  gt The type of model to save  lt  typeparam gt       lt param name  quot context quot  gt The database context tracking changes  lt  param gt       lt param name  quot model quot  gt The model object to save  lt  param gt       lt param name  quot existing quot  gt The latest model data  lt  param gt  public static void SaveChanges lt T gt  this DbContext context  T model  T existing      where T   class       context CheckNotNull nameof context        model CheckNotNull nameof context         context Entry existing  CurrentValues SetValues model       context SaveChanges            lt summary gt      Saves changes to a detached model by comparing it with the latest data       lt  summary gt       lt typeparam name  quot T quot  gt The type of model to save  lt  typeparam gt       lt param name  quot context quot  gt The database context tracking changes  lt  param gt       lt param name  quot model quot  gt The model object to save  lt  param gt       lt param name  quot existing quot  gt The latest model data  lt  param gt       lt param name  quot cancellationToken quot  gt A cancellation token to cancel the operation  lt  param gt       lt returns gt  lt  returns gt  public static async Task SaveChangesAsync lt T gt  this DbContext context  T model  T existing  CancellationToken cancellationToken   default      where T   class       context CheckNotNull nameof context        model CheckNotNull nameof context         context Entry existing  CurrentValues SetValues model       await context SaveChangesAsync cancellationToken  ConfigureAwait false

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Here is my code that works just fine   public async Task lt bool gt  UpdateDeviceShutdownAsync Guid id  DateTime shutdownAtTime  int areaID  decimal mileage          decimal motohours  int driverID  List lt int gt  commission          string shutdownPlaceDescr  int deviceShutdownTypeID  string deviceShutdownDesc          bool isTransportation  string violationConditions  DateTime shutdownStartTime          DateTime shutdownEndTime  string notes  List lt Guid gt  faultIDs                         try                               using  var db   new GJobEntities                                          var isExisting   await db DeviceShutdowns FirstOrDefaultAsync x   gt  x ID    id                        if  isExisting    null                                                isExisting AreaID   areaID                          isExisting DriverID   driverID                          isExisting IsTransportation   isTransportation                          isExisting Mileage   mileage                          isExisting Motohours   motohours                          isExisting Notes   notes                                              isExisting DeviceShutdownDesc   deviceShutdownDesc                          isExisting DeviceShutdownTypeID   deviceShutdownTypeID                          isExisting ShutdownAtTime   shutdownAtTime                          isExisting ShutdownEndTime   shutdownEndTime                          isExisting ShutdownStartTime   shutdownStartTime                          isExisting ShutdownPlaceDescr   shutdownPlaceDescr                          isExisting ViolationConditions   violationConditions                              Delete children                         foreach  var existingChild in isExisting DeviceShutdownFaults ToList                                                          db DeviceShutdownFaults Remove existingChild                                                      if  faultIDs    null  amp  amp  faultIDs Any                                                          foreach  var faultItem in faultIDs                                                                var newChild   new DeviceShutdownFault                                                                       ID   Guid NewGuid                                        DDFaultID   faultItem                                      DeviceShutdownID   isExisting ID                                                                      isExisting DeviceShutdownFaults Add newChild                                                                                       Delete all children                         foreach  var existingChild in isExisting DeviceShutdownComissions ToList                                                          db DeviceShutdownComissions Remove existingChild                                                         Add all new children                         if  commission    null  amp  amp  commission Any                                                          foreach  var cItem in commission                                                                var newChild   new DeviceShutdownComission                                                                       ID   Guid NewGuid                                        PersonalID   cItem                                      DeviceShutdownID   isExisting ID                                                                      isExisting DeviceShutdownComissions Add newChild                                                                                    await db SaveChangesAsync                             return true                                                                    catch  Exception ex                                logger Error ex                              return false

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Just proof of concept Controler UpdateModel won t work correctly   Full class here   const string PK    Id   protected Models Entities con  protected System Data Entity DbSet lt T gt  model   private void TestUpdate object item        var props   item GetType   GetProperties        foreach  var prop in props                object value   prop GetValue item           if  prop PropertyType IsInterface  amp  amp  value    null                        foreach  var iItem in  System Collections IEnumerable value                                TestUpdate iItem                                      int id    int item GetType   GetProperty PK  GetValue item       if  id    0                con Entry item  State   System Data Entity EntityState Added            else               con Entry item  State   System Data Entity EntityState Modified

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Charles McIntosh really gave me the answer for my situation in that the passed in model was detached  For me what ultimately worked was saving the passed in model first    then continuing to add the children as I already was before   public async Task lt IHttpActionResult gt  GetUPSFreight PartsExpressOrder order        db Entry order  State   EntityState Modified      db SaveChanges

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OK guys  I had this answer once but lost it along the way   absolute torture when you know there s a better way but can t remember it or find it  It s very simple   I just tested it multiple ways   var parent    dbContext Parents    Where p   gt  p Id    model Id     Include p   gt  p Children     FirstOrDefault     parent Children    dbContext Children Where c   gt   lt Query for New List Here gt     dbContext Entry parent  State   EntityState Modified    dbContext SaveChanges      You can replace the whole list with a new one   The SQL code will remove and add entities as needed   No need to concern yourself with that  Be sure to include child collection or no dice  Good luck

[c#] How to add/update child entities when updating a parent entity in EF

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