Why should I use IHttpActionResult instead of HttpResponseMessage

Question

I have been developing with WebApi and have moved on to WebApi2 where Microsoft has introduced a new IHttpActionResult Interface that seems to recommended to be used over returning a HttpResponseMessage  I am confused on the advantages of this new Interface  It seems to mainly just provide a SLIGHTLY easier way to create a HttpResponseMessage    I would make the argument that this is  abstraction for the sake of abstraction   Am I missing something  What is the real world advantages I get from using this new Interface besides maybe saving a line of code   Old way  WebApi    public HttpResponseMessage Delete int id        var status    Repository DeleteCustomer id       if  status                return new HttpResponseMessage HttpStatusCode OK             else               throw new HttpResponseException HttpStatusCode NotFound             New Way  WebApi2    public IHttpActionResult Delete int id        var status    Repository DeleteCustomer id       if  status                  return new HttpResponseMessage HttpStatusCode OK           return Ok              else                 throw new HttpResponseException HttpStatusCode NotFound           return NotFound

User · Answer

Here are several benefits of IHttpActionResult over HttpResponseMessage mentioned in Microsoft ASP Net Documentation           Simplifies unit testing your controllers    Moves common logic for creating HTTP responses into separate classes    Makes the intent of the controller action clearer  by hiding the low-level details of constructing the response       But here are some other advantages of using IHttpActionResult worth mentioning    Respecting single responsibility principle  cause action methods to have the responsibility of serving the HTTP requests and does not involve them in creating the HTTP response messages  Useful implementations already defined in the System Web Http Results namely  Ok NotFound Exception Unauthorized BadRequest Conflict Redirect InvalidModelState  link to full list  Uses Async and Await by default  Easy to create own ActionResult just by implementing ExecuteAsync method  you can use ResponseMessageResult ResponseMessage HttpResponseMessage response  to convert HttpResponseMessage to IHttpActionResult

User · Answer

The Web API basically return 4 type of object  void  HttpResponseMessage  IHttpActionResult  and other strong types  The first version of the Web API returns HttpResponseMessage which is pretty straight forward HTTP response message   The IHttpActionResult was introduced by WebAPI 2 which is a kind of wrap of HttpResponseMessage  It contains the ExecuteAsync   method to create an HttpResponseMessage  It simplifies unit testing of your controller    Other return type are kind of strong typed classes serialized by the Web API using a media formatter into the response body  The drawback was you cannot directly return an error code such as a 404  All you can do is throwing an HttpResponseException error

User · Answer

I d rather implement TaskExecuteAsync interface function for IHttpActionResult  Something like       public Task lt HttpResponseMessage gt  ExecuteAsync CancellationToken cancellationToken                var response    request CreateResponse HttpStatusCode InternalServerError   respContent            switch   Int32  respContent Code                         case 1              case 6              case 7                  response    request CreateResponse HttpStatusCode InternalServerError   respContent                   break              case 2              case 3              case 4                  response    request CreateResponse HttpStatusCode BadRequest   respContent                   break                      return Task FromResult response             where  request is the HttpRequest and  respContent is the payload

User · Answer

This is just my personal opinion and folks from web API team can probably articulate it better but here is my 2c   First of all  I think it is not a question of one over another  You can use them both depending on what you want to do in your action method but in order to understand the real power of IHttpActionResult  you will probably need to step outside those convenient helper methods of ApiController such as Ok  NotFound  etc   Basically  I think a class implementing IHttpActionResult as a factory of HttpResponseMessage  With that mind set  it now becomes an object that need to be returned and a factory that produces it  In general programming sense  you can create the object yourself in certain cases and in certain cases  you need a factory to do that  Same here   If you want to return a response which needs to be constructed through a complex logic  say lots of response headers  etc  you can abstract all those logic into an action result class implementing IHttpActionResult and use it in multiple action methods to return response   Another advantage of using IHttpActionResult as return type is that it makes ASP NET Web API action method similar to MVC  You can return any action result without getting caught in media formatters   Of course   as noted by Darrel  you can chain action results and create a powerful micro-pipeline similar to message handlers themselves in the API pipeline  This you will need depending on the complexity of your action method   Long story short - it is not IHttpActionResult versus HttpResponseMessage  Basically  it is how you want to create the response  Do it yourself or through a factory

User · Answer

You can still use HttpResponseMessage  That capability will not go away  I felt the same way as you and argued extensively with the team that there was no need for an additional abstraction  There were a few arguments thrown around to try and justify its existence but nothing that convinced me that it was worthwhile   That is  until I saw this sample from Brad Wilson   If you construct IHttpActionResult classes in a way that can be chained  you gain the ability to create a  action-level  response pipeline for generating the HttpResponseMessage   Under the covers  this is how ActionFilters are implemented however  the ordering of those ActionFilters is not obvious when reading the action method which is one reason I m not a fan of action filters   However  by creating an IHttpActionResult that can be explicitly chained in your action method you can compose all kinds of different behaviour to generate your response

User · Answer

You might decide not to use IHttpActionResult because your existing code builds a HttpResponseMessage that doesn t fit one of the canned responses   You can however adapt HttpResponseMessage to IHttpActionResult using the canned response of ResponseMessage   It took me a while to figure this out  so I wanted to post it showing that you don t necesarily have to choose one or the other   public IHttpActionResult SomeAction        IHttpActionResult response       we want a 303 with the ability to set location    HttpResponseMessage responseMsg   new HttpResponseMessage HttpStatusCode RedirectMethod      responseMsg Headers Location   new Uri  http   customLocation blah       response   ResponseMessage responseMsg      return response      Note  ResponseMessage is a method of the base class ApiController that your controller should inherit from

User · Answer

this will return HttpResponseMessage as IHttpActionResult return ResponseMessage httpResponseMessage

User · Answer

We have the  following benefits of using IHttpActionResult over  HttpResponseMessage    By using the IHttpActionResult we are only concentrating on the data to be send not on the status code  So here the code will be cleaner and very easy to maintain  Unit testing of the implemented controller method will be easier  Uses async and await by default

[c#] Why should I use IHttpActionResult instead of HttpResponseMessage?

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