MVC 4, Upshot entities cyclic references

Question

I have a DbDataController which delivers a List of Equipment.

    public IQueryable<BettrFit.Models.Equipment> GetEquipment() {
        var q= DbContext.EquipmentSet.OrderBy(e => e.Name);
        return q;
    }

In my scaffolded view everything looks ok.

But the Equipment contains a HashSet member of EquipmentType. I want to show this type in my view and also be able to add data to the EquipmentType collection of Equipment (via a multiselect list).

But if I try to include the "EquipmentType" in my linq query it fails during serialisation.

    public IQueryable<BettrFit.Models.Equipment> GetEquipment() {
        var q= DbContext.EquipmentSet.Include("EquipmentType").OrderBy(e => e.Name);
        return q;
    }

"Object Graph for Type EquipmentType Contains Cycles and Cannot be Serialized if Reference Tracking is Disabled"

How can I switch on the "backtracking of references"?

Maybe the problem is that the EquipmentType is back-linking through a HashSet? But I do not .include("EquipmentType.Equipment") in my query. So that should be ok.

How is Upshot generating the model? I only find the EquipmentViewModel.js file but this does not contain any model members.

Here are my model classes:

public class Equipment
{
    public Equipment()
    {
        this.Exercise = new HashSet<Exercise>();
        this.EquipmentType = new HashSet<EquipmentType>();
        this.UserDetails = new HashSet<UserDetails>();
    }

    public int ID { get; set; }
    public string Name { get; set; }
    public string Description { get; set; }
    public string Picture { get; set; }
    public string Link { get; set; }
    public string Producer { get; set; }
    public string Video { get; set; }

    public virtual ICollection<EquipmentType> EquipmentType { get; set; }
    public virtual ICollection<UserDetails> UserDetails { get; set; }
}
public class EquipmentType
{
    public EquipmentType()
    {
        this.Equipment = new HashSet<Equipment>();
        this.UserDetails = new HashSet<UserDetails>();
    }

    public int ID { get; set; }
    public string Name { get; set; }
    public string Description { get; set; }

    public virtual ICollection<Equipment> Equipment { get; set; }
    public virtual ICollection<UserDetails> UserDetails { get; set; }
}

Answer 1

I figured out - partially how to solve the circular reference problem.

I just iterated over my queried collection (with Include() ) and set the backreferences to the parent to NULL. That worked for the serialisation issue which otherwise already breaks on the server.

The only problem now is the update of a data entity - its failing because the arrays of the referenced entitycollection are static...

Answer 2

To solve the cyclic backreference, you can use the IgnoreDataMember attribute. Or you can set the back reference to NULL before returning the data from the DbDataController

I posted a working solution to your problem in a different question, but using Entity Framework Code First. https://stackoverflow.com/a/10010695/1226140

Here I show how to generate your client-side model manually, allowing to you to map the data however you please

Answer 3

try decorating one of the navigation properties with [IgnoreDataMember]

[IgnoreDataMember]
public virtual ICollection<Equipment> Equipment { get; set; } 

Answer 4

The model generated by upshot can be found on the page itself. In your Index view you will see the UpshotContext HTML helper being used (given that you are using the latest SPA version), in which the dataSource and model type are specified.

When the page is then rendered in the browser, this helper code is replaced with the actual model definition. To see that, view the source code of your page in the browser and search for a <script> tag that starts with upshot.dataSources = upshot.dataSources || {};

Check here for more info about how upshot generates the client side model. As for the "backtracking of references", I don't know :)