Return a WCF EF4 Entity as JSON - wcf

Question

My service interface is:
[ServiceContract]
public interface IMyService
{
[OperationContract]
[WebInvoke(Method = "GET", ResponseFormat = WebMessageFormat.Json, BodyStyle = WebMessageBodyStyle.Bare, UriTemplate = "HelloJSON/{name}")]
string HelloJSON(string name);
[OperationContract]
[WebInvoke(Method = "GET", ResponseFormat = WebMessageFormat.Json, BodyStyle = WebMessageBodyStyle.Bare, UriTemplate = "GetEmployees")]
List<Employee> GetEmployees();
}
My implementation is:
public class MyService : IMyService
{
public string HelloJSON(string name)
{
return string.Format("Hello {0} in JSON", name);
}
public List<Employee> GetEmployees()
{
using (DBEntities ctx = new DBEntities())
{
List<Employee> emp = new List<Employee>();
emp = (from e in ctx.Employee select e).ToList();
return emp;
}
}
}
When I call the first method I get something like "Hello pepe in JSON", that's ok.
When I call the second method and set a breakpoint on line "return emp;" I get the list of the employees(there are 6 records from the database), but in IE I get this:
Internet Explorer cannot display the webpage
and testing in Firefox all I get is a blank page with a blank body, no HTML, no data and no errors.
I think WCF can't serialize my default EF4 entities.
EDIT:
My final solution was something(not exactly) like this:
static string SerializeJSON<T>(T obj) {
JavaScriptSerializer serializer = new JavaScriptSerializer();
return serializer.Serialize(obj); }

Answer 1

EF entities cannot be serialized by default you must add code generation to them.
Refer to this article on how to create Serializable entities.
called Self Tracking entities

Answer 2

The best way would be to enable RIA Services and expose JSON Endpoint, it does everything correctly.
http://blogs.msdn.com/b/davrous/archive/2010/12/14/how-to-open-a-wcf-ria-services-application-to-other-type-of-clients-the-json-endpoint-4-5.aspx
http://channel9.msdn.com/Shows/SilverlightTV/Silverlight-TV-26-Exposing-SOAP-OData-and-JSON-Endpoints-for-RIA-Services