问Web API 2序列化程序选择

EN

public class ConverterController : ApiController
{
    class A {}
    public class B {}
    public class C : Exception {}

    public IHttpActionResult Action()
    {
       var res = Request.CreateResponse(HttpStatusCode.Ok, new A());
       // res.Content.Headers.ContentType.MediaType == "application/json"

       var res = Request.CreateResponse(HttpStatusCode.Ok, new B());
       // res.Content.Headers.ContentType.MediaType == "application/xml"

       var res = Request.CreateResponse(HttpStatusCode.Ok, new C());
       // res.Content.Headers.ContentType.MediaType == "application/json"
    }
}