silverlight domain service don't allow return a generic object - wcf

Question

I have a domain service running smooth, some expose functions that return generic lists of defined entity, but for some reason, I had add some common information so I created a generic object to wrap the collection with the extra information that I need return.
but when after made the change and try use the service in the client, the function don't show up in the context, I already search about it and what I found was attributes for generic IQueryable
my wrap class
public class Wrap<T>
{
public String commonProperty { get; set; }
public String anotherCommonProperty { get; set; }
public List<T> items { get; set; }
}
in my service domain
public Wrap<SomeClass> GetAll()
{
Wrap<SomeClass> myObject = new Wrap<SomeClass>();
myObject.items = new List<SomeClass>();
myObject.commonProperty = "some info";
myObject.anotherCommonProperty = "some info";
return myObject;
}

Answer 1

Maybe adding the [KnownType(typeof(SomeClass))] attribute in the Wrap<T> class, the problem is that you need to include one KnowType attribute for every class in your domain (this is because you are making a polymorphic service).
And adding the [ServiceKnownType(typeof(SomeClass))] in the GetAll method in the service (this is for wcf services I don't know if is valid for domain services).

Answer 2

WCF RIA domain services does not support generic entity types. IEnumerable<T> and IQueryable<T> are special cases.
Your method was ignored because it did not match supported method type.
Before changes GetAll was recognized as Query method. You can force that by adding attribute.
[Query]
public Wrap<SomeClass> GetAll()
Now it does not dissapear silently. But generates compile time error instead:
Type 'Wrap`1' is not a valid entity type. Entity types cannot be
generic.