ASP.NET MVC4 常见问题集

1. HttpResponseMessage<T> 泛型取消

We are working on a blog explaining the changes in HttpResponseMessage<T>, HttpRequestMessage<T>, and ObjectContent<T> in more details as we have simplified a bunch and made things more consistent.

The reason for the changes was that we ran into some issues with the HttpResponseMessage<T> and HttpRequestMessage<T> model. First, it was not possible to guarantee that the <T> carried in the HttpContent in a request or response actually was a <T>. As requests and responses are completely mutable they can contain any HttpContent implementation without any regard to HttpResponseMessage<T> or HttpRequestMessage<T>.

Second, HttpResponseMessage<T> and HttpRequestMessage<T> behaved slightly different depending on whether they were used on client side or server side.

Third, we wanted to make the common case simpler so that you always see HttpRequestMessage and HttpResponseMessage instances and not have to worry about whether they were generic or not. Now they are always the same.

Here’s a rough mapping from the old to the new model:

On the client side, all you now do when wanting to PUT or POST JSON (or XML) is to use these methods exposed directly on HttpClient:

HttpClient.PostAsJsonAsync<T>(T value) sends “application/json”

HttpClient.PostAsXmlAsync<T>(T value) sends “application/xml”

On the server side, in a controller you

ApiController.Request.CreateResponse<T> (T) sends content in the best format determined by content negotiation

You can also say: I want to send it in JSON explicitly in which case we will do that:

ApiController.Request.CreateResponse<T> (T, “application/json”) sends content in “application/json”

You can also cook up an ObjectContent yourself where you are in complete control of the formatter you want to use

HttpResponseMessage response = new HttpResponseMessage();

response.Content = new ObjectContent<T>(T, myFormatter, “application/some-format”);

Hope this helps – as I said we will be sending out more details on this.

public HttpResponseMessage PostReservation(Reservation reservation)
        {
            if (ModelState.IsValid)
            {
                db.Reservations.Add(reservation);
                db.SaveChanges();

                HttpResponseMessage response = Request.CreateResponse(HttpStatusCode.Created, reservation);
                response.Headers.Location = new Uri(Url.Link("DefaultApi", new { id = reservation.ReservationID }));
                return response;
            }
            else
            {
                return Request.CreateResponse(HttpStatusCode.BadRequest);
            }
        }