WCF REST service not returning DataContract object - wcf

Question

I have a simple WCF service defined by the following ServiceContract:
[ServiceContract]
public interface IInventoryService
{
[OperationContract]
Item GetItemFromBarcode(string barcode);
[OperationContract]
string Test(string testString);
}
With Item defined like this:
[DataContract]
public class Item
{
[DataMember]
public virtual int Id { get; set; }
<Snip>
}
And the actual service implemented thusly:
public class InventoryService : IInventoryService
{
[WebGet(UriTemplate = "/Barcode/{barcode}/Item", ResponseFormat = WebMessageFormat.Json)]
public Item GetItemFromBarcode(string barcode)
{
var item = (from b in repository.Query<ItemBarcode>()
where b.BarcodeData == barcode
select b.Item).FirstOrDefault();
return item;
}
[WebGet(UriTemplate = "/Test/{testString}",ResponseFormat=WebMessageFormat.Xml)]
public string Test(string testString)
{
return testString;
}
}
With the following in the app.config for the program hosting the service:
<system.serviceModel>
<behaviors>
<serviceBehaviors>
<behavior>
<serviceMetadata httpGetEnabled="true"/>
</behavior>
</serviceBehaviors>
<endpointBehaviors>
<behavior name="RESTFriendly">
<webHttp />
</behavior>
</endpointBehaviors>
</behaviors>
<services>
<service name="InventoryService">
<endpoint address="/Inventory" behaviorConfiguration="RESTFriendly" binding="webHttpBinding" contract="IInventoryService"/>
<host>
<baseAddresses>
<add baseAddress="http://localhost:8080/"/>
</baseAddresses>
</host>
</service>
</services>
</system.serviceModel>
Now that the code dump is out of the way, the issue: I can invoke the Test method just fine with curl or Fiddler, it returns a serialized string. However, invoking the method that returns an object returns nothing. Curl spits back curl: (56) Failure when receiving data from the peer and Fiddler responds ReadResponse() failed: The server did not return a response for this request.
From what I read, this should Just Work (tm). Is there something obvious I'm missing?

Answer 1

So, it seems you can't have DataMember of an interface type, like the IList<ItemBarcode>. There go my hopes of using my NHibernate model objects as DTOs.