Entity framework self referencing loop detected

Question

I have a strange error  I m experimenting with a  NET 4 5 Web API  Entity Framework and MS SQL Server  I ve already created the database and set up the correct primary and foreign keys and relationships   I ve created a  edmx model and imported two tables  Employee and Department  A department can have many employees and this relationship exists  I created a new controller called EmployeeController using the scaffolding options to create an API controller with read write actions using Entity Framework  In the wizard  selected Employee as the model and the correct entity for the data context   The method that is created looks like this   public IEnumerable lt Employee gt  GetEmployees         var employees   db Employees Include e   gt  e Department       return employees AsEnumerable        When I call my API via  api Employee  I get this error      The  ObjectContent 1  type failed to serialize the response body for content type  application json     System InvalidOperationException   StackTrace  null  InnerException    Message   An error has occurred    ExceptionMessage   Self referencing loop detected with type  System Data Entity DynamicProxies Employee 5D80AD978BC68A1D8BD675852F94E8B550F4CB150ADB8649E8998B7F95422552   Path   0  Department Employees     ExceptionType   Newtonsoft Json JsonSerializationException   StackTrace            Why is it self referencing  0  Department Employees  That doesn t make a whole lot of sense  I would expect this to happen if I had circular referencing in my database but this is a very simple example  What could be going wrong

User · Answer

I just had the same issue on my  net core site  The accepted answer didn t work for me but i found that a combination of ReferenceLoopHandling Ignore and PreserveReferencesHandling Objects fixed it     serialize item var serializedItem   JsonConvert SerializeObject data  Formatting Indented   new JsonSerializerSettings        PreserveReferencesHandling   PreserveReferencesHandling Objects       ReferenceLoopHandling   ReferenceLoopHandling Ignore

User · Answer

I m aware that question is quite old  but it s still popular and I can t see any solution for ASP net Core   I case of ASP net Core  you need to add new JsonOutputFormatter in Startup cs file       public void ConfigureServices IServiceCollection services                 services AddMvc options   gt                        options OutputFormatters Clear                options OutputFormatters Add new JsonOutputFormatter new JsonSerializerSettings                                 ReferenceLoopHandling   ReferenceLoopHandling Ignore                 ArrayPool lt char gt  Shared                                       After implementing it  JSON serializer will simply ignore loop references  What it means is  it will return null instead of infinitely loading objects referencing each other   Without above solution using   var employees   db Employees ToList      Would load Employees and related to them Departments   After setting ReferenceLoopHandling to Ignore  Departments will be set to null unless you include it in your query   var employees   db Employees Include e   gt  e Department     Also  keep in mind that it will clear all OutputFormatters  if you don t want that you can try removing this line   options OutputFormatters Clear      But removing it causes again self referencing loop exception in my case for some reason

User · Answer

If you are trying to change this setting in the Blazor  ASP NET Core Hosted  template  you need to pass the following to the AddNewtonsoftJson call in Startup cs in the Server project   services AddMvc   AddNewtonsoftJson options   gt       options SerializerSettings ReferenceLoopHandling   ReferenceLoopHandling Ignore

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The main problem is that serializing an entity model which has relation with other entity model Foreign key relationship   This relation causes self referencing this will throw exception while serialization to json or xml  There are lots of options  Without serializing entity models by using custom models Values or data from entity model data mapped to custom models object mapping  using Automapper or Valueinjector then return request and it will serialize without any other issues  Or you can serialize entity model so first disable proxies in entity model   public class LabEntities   DbContext      public LabEntities              Configuration ProxyCreationEnabled   false         To preserve object references in XML  you have two options  The simpler option is to add  DataContract IsReference true   to your model class  The IsReference parameter enables oibject references  Remember that DataContract makes serialization opt-in  so you will also need to add DataMember attributes to the properties    DataContract IsReference true   public partial class Employee       DataMember     string dfsd get set       DataMember     string dfsd get set        exclude  the relation without giving datamember tag    List lt Department gt  Departments get set       In Json format in global asax  var json   GlobalConfiguration Configuration Formatters JsonFormatter  json SerializerSettings PreserveReferencesHandling        Newtonsoft Json PreserveReferencesHandling All    in xml format  var xml   GlobalConfiguration Configuration Formatters XmlFormatter  var dcs   new DataContractSerializer typeof Employee   null  int MaxValue       false     preserveObjectReferences     true  null   xml SetSerializer lt Employee gt  dcs

User · Answer

The message error means that you have a self referencing loop   The json you produce is like this example  with a list of one employee       employee1         name   name       department             name   departmentName           employees                 employee1                     name   name                   department                         name   departmentName                       employees                             employee1                                 name   name                               department                                     and again and again                                                                                                                You have to tell the db context that you don t want to get all linked entities when you request something  The option for DbContext is Configuration LazyLoadingEnabled  The best way I found is to create a context for serialization    public class SerializerContext   LabEntities        public SerializerContext                 this Configuration LazyLoadingEnabled   false

User · Answer

Self-referencing as example  public class Employee       public int Id   get  set        public string FirstName   get  set        public string LastName   get  set        public string Email   get  set        public int ManagerId   get  set        public virtual Employee Manager   get  set         public virtual ICollection lt Employee gt  Employees   get  set         public Employee             Employees   new HashSet lt Employee gt               HasMany e   gt  e Employees       WithRequired e   gt  e Manager       HasForeignKey e   gt  e ManagerId       WillCascadeOnDelete false

User · Answer

I might also look into adding explicit samples for each controller action  as well covered here   http   blogs msdn com b yaohuang1 archive 2012 10 13 asp-net-web-api-help-page-part-2-providing-custom-samples-on-the-help-page aspx  i e  config SetActualResponseType typeof SomeType    Values    Get

User · Answer

Well the correct answer for the default Json formater based on Json net is to set ReferenceLoopHandling to Ignore   Just add this to the Application Start in Global asax   HttpConfiguration config   GlobalConfiguration Configuration   config Formatters JsonFormatter              SerializerSettings              ReferenceLoopHandling   Newtonsoft Json ReferenceLoopHandling Ignore    This is the correct way  It will ignore the reference pointing back to the object   Other responses focused in changing the list being returned by excluding data or by making a facade object and sometimes that is not an option   Using the JsonIgnore attribute to restrict the references can be time consuming and if you want to serialize the tree starting from another point that will be a problem

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I only had one model i wanted to use  so i ended up with the following code   var JsonImageModel   Newtonsoft Json JsonConvert SerializeObject Images  new JsonSerializerSettings   ReferenceLoopHandling   ReferenceLoopHandling Ignore

User · Answer

Add a line Configuration ProxyCreationEnabled   false  in constructor of your context model partial class definition       public partial class YourDbContextModelName   DbContext       public YourDbContextModelName             base  name YourDbContextConn StringName                 Configuration ProxyCreationEnabled   false   this is line to be added            public virtual DbSet lt Employee gt  Employees  get  set         protected override void OnModelCreating DbModelBuilder modelBuilder

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I know this is an old question but here is the solution I found to a very similar coding issue in my own code   var response   ApiDB Persons Include y   gt  y JobTitle  Include b   gt  b Discipline  Include b   gt  b Team  Include b   gt  b Site  OrderBy d   gt  d DisplayName  ToArray            foreach  var person in response                        person JobTitle   new JobTitle                                 JobTitle ID   person JobTitle JobTitle ID                  JobTitleName   person JobTitle JobTitleName                  PatientInteraction   person JobTitle PatientInteraction                  Active   person JobTitle Active                  IsClinical   person JobTitle IsClinical                            Since the person object contains everything from the person table and the job title object contains a list of persons with that job title  the database kept self referencing  I thought disabling proxy creation and lazy loading would fix this but unfortunately it didn t   For the that aren t able to do that  try the solution above  Explicitly creating a new object for each object that self references  but leave out the list of objects or object that goes back to the previous entity will fix it since disabling lazy loading does not appear to work for me

User · Answer

This happens because you re trying to serialize the EF object collection directly  Since department has an association to employee and employee to department  the JSON serializer will loop infinetly reading d Employee Departments Employee Departments etc     To fix this right before the serialization create an anonymous type with the props you want  example  psuedo code   departments select dep   gt  new        dep Id       Employee   new            dep Employee Id  dep Employee Name

User · Answer

I had same problem and found that you can just apply the  JsonIgnore  attribute to the navigation property you don t want to be serialised  It will still serialise both the parent and child entities but just avoids the self referencing loop

[c#] Entity framework self referencing loop detected

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