A circular reference was detected while serializing an object of type SubSonic Schema DatabaseColumn

Question

I am trying to do a simple JSON return but I am having issues I have the following below   public JsonResult GetEventData         var data   Event Find x   gt  x ID    0       return Json data       I get a HTTP 500 with the exception as shown in the title of this question  I also tried  var data   Event All   ToList     That gave the same problem   Is this a bug or my implementation

User · Answer

An easier alternative to solve this problem is to return an string, and format that string to json with JavaScriptSerializer.

public string GetEntityInJson()
{
   JavaScriptSerializer j = new JavaScriptSerializer();
   var entityList = dataContext.Entitites.Select(x => new { ID = x.ID, AnotherAttribute = x.AnotherAttribute });
   return j.Serialize(entityList );
}

It is important the "Select" part, which choose the properties you want in your view. Some object have a reference for the parent. If you do not choose the attributes, the circular reference may appear, if you just take the tables as a whole.

Do not do this:

public string GetEntityInJson()
{
   JavaScriptSerializer j = new JavaScriptSerializer();
   var entityList = dataContext.Entitites.toList();
   return j.Serialize(entityList );
}

Do this instead if you don't want the whole table:

public string GetEntityInJson()
{
   JavaScriptSerializer j = new JavaScriptSerializer();
   var entityList = dataContext.Entitites.Select(x => new { ID = x.ID, AnotherAttribute = x.AnotherAttribute });
   return j.Serialize(entityList );
}

This helps render a view with less data, just with the attributes you need, and makes your web run faster.

User · Answer

You can notice the properties that cause the circular reference  Then you can do something like   private Object DeCircular Object object          Set properties that cause the circular reference to null     return object

User · Answer

JSON  like xml and various other formats  is a tree-based serialization format  It won t love you if you have circular references in your objects  as the  tree  would be   root B   gt  child A   gt  parent B   gt  child A   gt  parent B   gt        There are often ways of disabling navigation along a certain path  for example  with XmlSerializer you might mark the parent property as XmlIgnore  I don t know if this is possible with the json serializer in question  nor whether DatabaseColumn has suitable markers  very unlikely  as it would need to reference every serialization API

User · Answer

This actually happens because the complex objects are what makes the resulting json object fails  And it fails because when the object is mapped it maps the children  which maps their parents  making a circular reference to occur  Json would take infinite time to serialize it  so it prevents the problem with the exception   Entity Framework mapping also produces the same behavior  and the solution is to discard all unwanted properties   Just expliciting the final answer  the whole code would be   public JsonResult getJson         DataContext db   new DataContext          return this Json             new                   Result    from obj in db Things select new  Id   obj Id  Name   obj Name                                 JsonRequestBehavior AllowGet                   It could also be the following in case you don t want the objects inside a Result property   public JsonResult getJson         DataContext db   new DataContext          return this Json              from obj in db Things select new  Id   obj Id  Name   obj Name                JsonRequestBehavior AllowGet

User · Answer

Provided answers are good  but I think they can be improved by adding an  architectural  perspective   Investigation  MVC s Controller Json function is doing the job  but it is very poor at providing a relevant error in this case  By using Newtonsoft Json JsonConvert SerializeObject  the error specifies exactly what is the property that is triggering the circular reference  This is particularly useful when serializing more complex object hierarchies   Proper architecture  One should never try to serialize data models  e g  EF models   as ORM s navigation properties is the road to perdition when it comes to serialization  Data flow should be the following   Database - gt  data models - gt  service models - gt  JSON string    Service models can be obtained from data models using auto mappers  e g  Automapper   While this does not guarantee lack of circular references  proper design should do it  service models should contain exactly what the service consumer requires  i e  the properties    In those rare cases  when the client requests a hierarchy involving the same object type on different levels  the service can create a linear structure with parent- child relationship  using just identifiers  not references    Modern applications tend to avoid loading complex data structures at once and service models should be slim  E g     access an event - only header data  identifier  name  date etc   is loaded -  service model  JSON  containing only header data managed attendees list - access a popup and lazy load the list -  service model  JSON  containing only the list of attendees

User · Answer

To sum things up  there are 4 solutions to this   Solution 1  turn off ProxyCreation for the DBContext and restore it in the end        private DBEntities db   new DBEntities     dbcontext      public ActionResult Index                 bool proxyCreation   db Configuration ProxyCreationEnabled          try                         set ProxyCreation to false             db Configuration ProxyCreationEnabled   false               var data   db Products ToList                 return Json data  JsonRequestBehavior AllowGet                     catch  Exception ex                        Response StatusCode    int HttpStatusCode BadRequest              return Json ex Message                     finally                         restore ProxyCreation to its original state             db Configuration ProxyCreationEnabled   proxyCreation                    Solution 2  Using JsonConvert by Setting ReferenceLoopHandling to ignore on the serializer settings          using using Newtonsoft Json       private DBEntities db   new DBEntities     dbcontext      public ActionResult Index                 try                       var data   db Products ToList                 JsonSerializerSettings jss   new JsonSerializerSettings   ReferenceLoopHandling   ReferenceLoopHandling Ignore                var result   JsonConvert SerializeObject data  Formatting Indented  jss                return Json result  JsonRequestBehavior AllowGet                     catch  Exception ex                        Response StatusCode    int HttpStatusCode BadRequest              return Json ex Message                     Following two solutions are the same  but using a model is better because it s strong typed   Solution 3  return a Model which includes the needed properties only       private DBEntities db   new DBEntities     dbcontext      public class ProductModel               public int Product ID   get  set            public string Product Name   get  set            public double Product Price   get  set              public ActionResult Index                 try                       var data   db Products Select p   gt  new ProductModel                                                                                                       Product ID   p Product ID                                                      Product Name   p Product Name                                                      Product Price   p Product Price                                                    ToList                 return Json data  JsonRequestBehavior AllowGet                     catch  Exception ex                        Response StatusCode    int HttpStatusCode BadRequest              return Json ex Message                     Solution 4  return a new dynamic object which includes the needed properties only       private DBEntities db   new DBEntities     dbcontext      public ActionResult Index                 try                       var data   db Products Select p   gt  new                                                                                                       Product ID   p Product ID                                                      Product Name   p Product Name                                                      Product Price   p Product Price                                                    ToList                 return Json data  JsonRequestBehavior AllowGet                     catch  Exception ex                        Response StatusCode    int HttpStatusCode BadRequest              return Json ex Message

User · Answer

I m Using the fix  Because Using Knockout in MVC5 views   On action  return Json ModelHelper GetJsonModel lt Core User gt  viewModel      function     public static TEntity GetJsonModel lt TEntity gt  TEntity Entity  where TEntity   class               TEntity Entity    Activator CreateInstance typeof TEntity   as TEntity          foreach  var item in Entity GetType   GetProperties                          if  item PropertyType ToString   IndexOf  Generic ICollection      -1  amp  amp  item PropertyType ToString   IndexOf  SaymenCore DAL       -1                  item SetValue Entity   Entity GetPropValue item Name                      return Entity

User · Answer

I had the same problem and solved by using Newtonsoft Json   var list   JsonConvert SerializeObject model      Formatting None      new JsonSerializerSettings             ReferenceLoopHandling   Newtonsoft Json ReferenceLoopHandling Ignore      return Content list   application json

User · Answer

first  Create a class as your view model  public class EventViewModel     public int Id get set   public string Property1 get set    public string Property2 get set       then from your method  HttpGet  public async Task lt ActionResult gt  GetEvent      var events   await db Event Find x   gt  x ID    0    List lt EventViewModel gt  model   events Select event   gt  new EventViewModel     Id   event Id   Property1   event Property1   Property1   event Property2    ToList     return Json new  data   model    JsonRequestBehavior AllowGet

User · Answer

Its because of the new DbContext T4 template that is used for generating the EntityFramework entities  In order to be able to perform the change tracking  this templates uses the Proxy pattern  by wrapping your nice POCOs with them  This then causes the issues when serializing with the JavaScriptSerializer   So then the 2 solutions are    Either you just serialize and return the properties you need on the client You may switch off the automatic generation of proxies by setting it on the context s configuration  context Configuration ProxyCreationEnabled   false    Very well explained in the below article   http   juristr com blog 2011 08 javascriptserializer-circular-reference

User · Answer

Using Newtonsoft Json  In your Global asax Application Start method add this line   GlobalConfiguration Configuration Formatters JsonFormatter SerializerSettings ReferenceLoopHandling   Newtonsoft Json ReferenceLoopHandling Ignore

User · Answer

add  JsonIgnore  to virtuals properties in your model

User · Answer

It seems that there are circular references in your object hierarchy which is not supported by the JSON serializer  Do you need all the columns  You could pick up only the properties you need in the view   return Json new          PropertyINeed1   data PropertyINeed1      PropertyINeed2   data PropertyINeed2       This will make your JSON object lighter and easier to understand  If you have many properties  AutoMapper could be used to automatically map between DTO objects and View objects

User · Answer

Avoid converting the table object directly  If relations are set between other tables  it might throw this error  Rather  you can create a model class  assign values to the class object and then serialize it

[c#] A circular reference was detected while serializing an object of type 'SubSonic.Schema .DatabaseColumn'.

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