c# - EF 4.1 - Code First - JSON Circular Reference Serialization Error

Question

I am getting an a Circular Reference Serialization Error although, to my knowledge I do not have any circular references. I am retrieving a set of Orders from the database and sending them to the client as JSON. All the code is shown below.

This is the error:

Error

A circular reference was detected while serializing an object of type 'System.Data.Entity.DynamicProxies.Order_83CECF2AA4DE38232F9077D4B26941AB96BC61230419EA8AC42C9100E6072812'. Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.InvalidOperationException: A circular reference was detected while serializing an object of type 'System.Data.Entity.DynamicProxies.Order_83CECF2AA4DE38232F9077D4B26941AB96BC61230419EA8AC42C9100E6072812'.

Source Error:

An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.

My classes are as follows:

Order

public class Order
{
    [Key]
    public int OrderId { get; set; }

    public int PatientId { get; set; }
    public virtual Patient Patient { get; set; }

    public int CertificationPeriodId { get; set; }
    public virtual CertificationPeriod CertificationPeriod { get; set; }

    public int AgencyId { get; set; }
    public virtual Agency Agency { get; set; }

    public int PrimaryDiagnosisId { get; set; }
    public virtual Diagnosis PrimaryDiagnosis { get; set; }

    public int ApprovalStatusId { get; set; }
    public virtual OrderApprovalStatus ApprovalStatus { get; set; }

    public int ApproverId { get; set; }
    public virtual User Approver { get; set; }

    public int SubmitterId { get; set; }
    public virtual User Submitter { get; set; }

    public DateTime ApprovalDate { get; set; }

    public DateTime SubmittedDate { get; set; }
    public Boolean IsDeprecated { get; set; }
}

Patient

public class Patient
{
    [Key]
    public int PatientId { get; set; }
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public string MiddleInitial { get; set; }
    public bool IsMale;
    public DateTime DateOfBirth { get; set; }

    public int PatientAddressId { get; set; }
    public Address PatientAddress { get; set; }

    public bool IsDeprecated { get; set; }
}

Certification Period

public class CertificationPeriod
{
    [Key]
    public int CertificationPeriodId { get; set; }
    public DateTime startDate { get; set; }
    public DateTime endDate { get; set; }
    public bool isDeprecated { get; set; }
}

Agency

public class Agency
{
    [Key]
    public int AgencyId { get; set; }
    public string Name { get; set; }

    public int PatientAddressId { get; set; }
    public virtual Address Address { get; set; }
}

Diagnosis

public class Diagnosis
{
    [Key]
    public int DiagnosisId { get; set; }
    public string Icd9Code { get; set; }
    public string Description { get; set; }
    public DateTime DateOfDiagnosis { get; set; }
    public string Onset { get; set; }
    public string Details { get; set; }
}

OrderApprovalStatus

public class OrderApprovalStatus
{
    [Key]
    public int OrderApprovalStatusId { get; set; }
    public string Status { get; set; }
}

User

public class User
{
    [Key]
    public int UserId { get; set; }
    public string Login { get; set; }
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public string NPI { get; set; }
    public string Email { get; set; }

}

NOTE: ADDRESS CLASS IS NEW ADDITION DURING EDIT

Address

public class Address
{
    [Key]
    public int AddressId { get; set; }
    public string StreetAddress { get; set; }
    public string City { get; set; }
    public string State { get; set; }
    public string Zip { get; set; }
    public string Phone { get; set; }
    public string Title { get; set; }
    public string Label { get; set; }
}

The code that executes the serialization is here:

Excerpt from OrderController

    public ActionResult GetAll()
    {
        return Json(ppEFContext.Orders, JsonRequestBehavior.AllowGet);
    }

Thanks

Answer 1

You could try to remove the virtual keyword from all navigation properties to disable lazy loading and proxy creation and then use eager loading instead to load the required object graph explicitely:

public ActionResult GetAll()
{
    return Json(ppEFContext.Orders
                           .Include(o => o.Patient)
                           .Include(o => o.Patient.PatientAddress)
                           .Include(o => o.CertificationPeriod)
                           .Include(o => o.Agency)
                           .Include(o => o.Agency.Address)
                           .Include(o => o.PrimaryDiagnosis)
                           .Include(o => o.ApprovalStatus)
                           .Include(o => o.Approver)
                           .Include(o => o.Submitter),
        JsonRequestBehavior.AllowGet);
}

Referring to your previous post it looks like your application isn't relying on lazy loading anyway because you introduced there the virtual properties to load the object graph lazily, possibly causing now the serialization trouble.

Edit

It's not necessary to remove the virtual keyword from the navigation properties (which would make lazy loading completely impossible for the model). It's enough to disable proxy creation (which disables lazy loading as well) for the specific circumstances where proxies are disturbing, like serialization:

ppEFContext.Configuration.ProxyCreationEnabled = false;

This disables proxy creation only for the specific context instance ppEFContext.

(I've just seen, @WillC already mentioned it here. Upvote for this edit please to his answer.)