WCF - Entity framework, generated entities serialization error

Question

I'm new to WCF and today I have encountered a problem with DataContracts. I'm getting exception when objects are returned to client from WCF Service.

SvcTraceViewer shows the next exception:

Type 'System.Data.Entity.DynamicProxies.Person_7C797A477DD73534D4E8E743E1FCC1C75DAB75933D03B845A097A8B83F2DD748' with data contract name 'Person_7C797A477DD73534D4E8E743E1FCC1C75DAB75933D03B845A097A8B83F2DD748:http://schemas.datacontract.org/2004/07/System.Data.Entity.DynamicProxies' is not expected. Consider using a DataContractResolver or add any types not known statically to the list of known types - for example, by using the KnownTypeAttribute attribute or by adding them to the list of known types passed to DataContractSerializer.

I have several projects in solution.

• DataAccess (EntityFramework EDMX file is placed here)
• Model (Entities generated by DbContextGenerator are here)
• WCF Service (DataContracts are implemented in Model project)
• WPF Application (runs ServiceHost)
• Console Application (calls WCF project or service hosted in WPF Application)

Here is operation contract in WCF:

[OperationContract]
Person[] GetAllPersons(int version);

interface implementation:

public Person[] GetAllPersons(int version)
{
    return StorageService.GetAllPersons(version);
}

The excepion is thrown when the data is recieved on the client side (ConsoleApp).

I guess the problem is related to generated entities, because they are partial classes

Here is Person class:

public partial class Person
{
    public Person()
    {
        this.Project = new HashSet<Project>();
    }

    public int Id { get; set; }
    public Nullable<long> AddressId { get; set; }
    public string LastName { get; set; }
    public string MiddleName { get; set; }
    public string FirstName { get; set; }
    public Nullable<long> GeoLocationId { get; set; }
    public string FullGeoLocationName { get; set; }
    public Nullable<long> SupervisorId { get; set; }
    public Nullable<long> PositionId { get; set; }
    public string Position { get; set; }
    public string Office { get; set; }
    public string NativeName { get; set; }
    public string Location { get; set; }
    public string FullName { get; set; }
    public Nullable<long> PmcPersonId { get; set; }

    public virtual ICollection<Project> Project { get; set; }
    public virtual PersonDataVersion DataVersion { get; set; }
    public virtual Workspace Workspace { get; set; }
}

I tried to mark class and it's members with [DataContract] and [DataMember] attributes, but error still happens. [KnownType(typeof(Person)] attribute also didn't help.

Is it possible to use generated entities as data contracts?

Answer 1

DynamicProxies indicate that you are using lazy loading and the error could be caused by the context being closed when WCF tries to serialize the object.

Try disabling lazy loading and use eager loading instead.