Question

I am attempting to retrieve a list of objects from Entity Framework via WCF, but am receiving the following exception:

There was an error while trying to serialize parameter http://tempuri.org/:GetAllResult. The InnerException message was ‘Type ‘System.Data.Entity.DynamicProxies.TestObject_240F2B681A782799F3A0C3AFBE4A67A7E86083C3CC4A3939573C5410B408ECCE’ with data contract name ‘TestObject_240F2B681A782799F3A0C3AFBE4A67A7E86083C3CC4A3939573C5410B408ECCE: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.’. Please see InnerException for more details.

I have used WCF in the past, but never with Entity Framework. I have all my entities generated via Entity Framework and are annotated with [DataContract] and [DataMember] attributes. I have no Navigation Properties on any of my entities.

The GetAll() method being called is in an abstract service class:

[ServiceContract]
public interface IService<T>
{
    [OperationContract]
    List<T> GetAll();
}

And I am using the ChannelFactory to call my implementation:

Binding binding = new NetTcpBinding();
EndpointAddress endpointAddress = new EndpointAddress("net.tcp://localhost:8081/" + typeof(TestObjectService).Name);
using (ChannelFactory<ITestObjectService> channel = new ChannelFactory<ITestObjectService>(binding, endpointAddress))
{
    ITestObjectService testObjectService = channel.CreateChannel();
    testObjects = testObjectService.GetAll();
    channel.Close();
}

I am hosting it as such:

Type type = typeof(TestObjectService);
ServiceHost host = new ServiceHost(type,
            new Uri("http://localhost:8080/" + type.Name),
            new Uri("net.tcp://localhost:8081/" + type.Name));
host.Open();

When using debugging, it finds the objects from the database, however, it is failing returning the objects.

Any ideas as to where I may be going wrong?

Answer 1

This was a pain to figure out but it is because EntityFramework creates a ‘proxy’ of your class. The TestObject class I had was setup correctly, but it was creating a class called: TestObject_240F2B681A782799F3A0C3AFBE4A67A7E86083C3CC4A3939573C5410B408ECCE

To make the ChannelFactory + WCF + Entity Framework all work together, you must go into your Context constructor and add the following:

ContextOptions.ProxyCreationEnabled = false;