circular reference while serializing json

[Richard]

 I have a problem, as the following

Using sample: "Sofia Car Rental ASP.NET Ajax integration example with OpenAccess"

            SofiaCarRental.DAL.SofiaCarRentalContext context = new SofiaCarRental.DAL.SofiaCarRentalContext();
            List<SofiaCarRental.DAL.Category> ls = context.Categories.ToList();
            System.Web.Script.Serialization.JavaScriptSerializer jss = new System.Web.Script.SerializationJavaScriptSerializer();
            string output = jss.Serialize(ls);

// Exception 

Circular reference was detected while serializing an object of type 'SofiaCarRental.DAL.Category'.

 It solves disabling "Target end" a the Category. How do I set the model from the beginning, in the creation of rlinq

[Dimitar Tachev]

Hi Richard,

 
Removing one of the ends of the associations between the problematic entities is a possible solution for this problem but its disadvantage is that you are loosing a lot of references between the domain classes of your model.

In order to convert the Categories from you context instance to their JSON string representation I suggest you the following approach using the JSON.NET library which could also be downloaded as a Nuget package:

string jsonData = string.Empty;

 

// get JSON string from the categories

using (EntitiesModel context = new EntitiesModel())

{

    // specify the fetch plan for the detaching

    FetchStrategy fetchStrategy = new FetchStrategy();

    fetchStrategy.LoadWith<Category>(c => c.Products);

    fetchStrategy.LoadWith<Product>(p => p.OrderDetails);

 

    // detach the categories with their products and the order details
      //along with the products (without the opposite references)

    IList<Category> categories = context.Categories.ToList();

    var detachedCategories =
context.CreateDetachedCopy<Category>(categories, fetchStrategy);

 

    // avoid getting error for possible circular references

    JsonSerializerSettings serializationSettings = new JsonSerializerSettings()

    {

        ReferenceLoopHandling = ReferenceLoopHandling.Ignore

    };

 

    // convert the detached categories along with their products
      // and OrderDetails to JSON string

    jsonData =
JsonConvert.SerializeObject(detachedCategories, serializationSettings);

}

 

// ....

// pass the JSON string to the client for some CRUD
// operations and return a JSON string again

// ....

 

// attach the categories from the JSON string

using (EntitiesModel context = new EntitiesModel())

{

    // convert the JSON string to list of Category objects
      // along with the Products and their OrderDetails

    List<Category> deserializedCategories = JsonConvert.DeserializeObject<List<Category>>(jsonData);

 

    foreach (Category category in deserializedCategories)

    {

        // attach each of the categories to a context instance (the context
   // can be the same or different from the previous one)

        // in order to track the changes and resolve again all
   //of the references from the objects graph

        context.AttachCopy<Category>(category);

    }

 

    // commit the changes from the JSON string to the database

    context.SaveChanges();

}

Choosing this approach you will not need to remove some ends of your associations because you could specify only the navigation properties that you need in the FetchPlan and disable the loop handling validation of the JSON.NET converter.

If this is not applicable for you and you want to use the JavaScriptSerializer I believe that you will need to manually remove the problematic association ends - there isn't a global setting for removing one of the ends.

I hope this helps. Do not hesitate to contact us back if you need any further assistance.


Regards,
Dimitar Tachev
Telerik