Question

I just started a new Silverlight project with Visual Studio Express 2012 for Web.

I created a Silverlight-enabled WCF service to access a SQL Server database, with EF 5.

The problem I’m having is that the service doesn’t seem to be able to return any entity retrieved from the database. A new entity or any old object is returned just fine, but when I try to return an entity from the context I get the following exception:

{System.ServiceModel.CommunicationException: The remote server returned an error: NotFound. --->      System.Net.WebException: The remote server returned an error: NotFound. ---> System.Net.WebException:  The remote server returned an error: NotFound.
   at System.Net.Browser.BrowserHttpWebRequest.InternalEndGetResponse(IAsyncResult asyncResult)
   at System.Net.Browser.BrowserHttpWebRequest.<>c__DisplayClassa.<EndGetResponse>b__9(Object sendState)
   at System.Net.Browser.AsyncHelper.<>c__DisplayClass4.<BeginOnUI>b__0(Object sendState)
   --- End of inner exception stack trace ---
   at System.Net.Browser.AsyncHelper.BeginOnUI(SendOrPostCallback beginMethod, Object state)
   at System.Net.Browser.BrowserHttpWebRequest.EndGetResponse(IAsyncResult asyncResult)
   at System.ServiceModel.Channels.HttpChannelFactory.HttpRequestChannel.HttpChannelAsyncRequest.CompleteGetResponse(IAsyncResult result)
   --- End of inner exception stack trace ---
   at System.ServiceModel.AsyncResult.End[TAsyncResult](IAsyncResult result)
   at System.ServiceModel.Channels.ServiceChannel.EndCall(String action, Object[] outs, IAsyncResult result)
   at System.ServiceModel.ClientBase`1.ChannelBase`1.EndInvoke(String methodName, Object[] args, IAsyncResult result)
   at NewProj.DataSvcRef.DataServiceClient.DataServiceClientChannel.EndGetAgency(IAsyncResult result)
   at NewProj.DataSvcRef.DataServiceClient.NewProj.DataSvcRef.DataService.EndGetAgency(IAsyncResult result)
   at NewProj.DataSvcRef.DataServiceClient.OnEndGetAgency(IAsyncResult result)
   at System.ServiceModel.ClientBase`1.OnAsyncCallCompleted(IAsyncResult result)}

The service method code couldn’t be simpler:

[OperationContract]
public Contact GetContact(int aID)
{
  Contact res = null;
  using (var db = new OFBEntities())
  {
    try
    {
      res = db.Contacts.Find(aID);
    }
    catch (Exception ex)
    {
      res = null;
    }

    return res;
  }
}

As I mentioned, if I return a newly created object (return new Contact(){ name=”test contact};), or return a type that is not in context (say an integer for example), everything works fine.

Is this a limitation of the express version, or am I forgetting some settings? In the past I have created some Silverlight apps that consumed data services with VS 2010, Silverlight 4, and I don’t remember having to set anything special, but maybe I just forgot that I did?

Any help is appreciated!

EDIT:
Could it have anything to do with DbContext and the way it is serialized? I’ve never used DbContext before, I always used the default ObjectContext in EF 4…

EDIT2: SOLUTION
It’s been a while, but I had other things to work :o)
In case anybody is in the same boat, the problem was in the serialization by the service. DbContext by default creates proxies, which don’t agree with serialization. I am not sure why yet – indeed, I need to educate myself about those proxies – but disabling them solves my serialization issue.
Thanks for the comment Pawel, I mistakenly thought my serialization was going OK, rechecking the server-side error put me back on the right track.

Answer 1

The problem was with automatic proxy creation by the DBContext, which interfered with the serialization.
Proxies are on by default in DBContext, you can disable them in the class constructor

  this.Configuration.ProxyCreationEnabled = false;

or after creating an instance of your DBContext

  using (var db = new myDBContext())
  {
    db.Configuration.ProxyCreationEnabled = false;

    ...
  }

Not sure why yet, but it works. Time to go read up on that!