Return a WCF EF4 Entity as JSON

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开发者_如何学JAVA 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); }

---

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

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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