Hi Bruce,

        When I sent my previous response, I have not read this one from you.       

        You have partially answered my questions.Thanks.

        I still have questions:

        (1) Does your comment regarding IHttpActionResult equally applicable to HttpResponseMessage?

        (2) About "will not work without writing custom model binder as binder can not create instance of interface", could you give a rough sketch of an example of a custom binder?

Thanks again,
Golden