Nick Riggs, Web Developer

Often times I’d like to provide simple JSON/XML API endpoints for my web application. When I first started using ASP.NET MVC, I’d create separate actions that would return a JSONActionResult. This worked, but always felt like code bloat in my controllers.

I also am an avid user of view models in my controllers – as models for my views and as parameters for my actions. Usually, my view models have only exactly what is needed for the view or action, and usually look nothing like the underlying model (data entities).

This got me thinking that my existing controller actions were already poised to be my API. I just needed to control the format in which they accepted and returned the view models. So I created MVC API Action Filter some time ago, and recently open sourced it.

As an example, let’s have a Create action that accepts a Person view model, modifies the databases and redirects to the Details action:

[HttpGet]
public ActionResult Create()
{
    return View(new Person());
}

[HttpPost]
public ActionResult Create(Person person)
{
    if (!ModelState.IsValid)
        return View(person);

    _data.Create(person);

    return RedirectToAction("Details", new { id = person.Id });
}

public ActionResult Details(Guid id)
{
    var person = _data.Get(id);

    return View(person);
}

This works fine using the Html form and displaying the details after the post:

Now let’s take the same actions and expose them as JSON/XML API endpoints. To do this, we simply decorate the actions with the [Api] attribute:

[HttpPost]
[Api]
public ActionResult Create(Person person)
...

[Api]
public ActionResult Details(Guid id)
...

To specify the format of the request, we modify the Content-Type header. To specify the format of the response, we modify the Accept header. Let’s use jQuery to demonstrate JSON example:

$.ajax({
   type: "POST",
   contentType: "text/json",
   dataType: "json",
   data: "{\"FirstName\":\"Nick\",\"LastName\":\"Riggs\",\"Age\":30}",
   url: "Home/Create"
});

The response looks like:

{"Id":"52536e05-9433-402b-948b-8560923d34b7","FirstName":"Nick","LastName":"Riggs","Age":30}

An XML example:

$.ajax({
   type: "POST",
   contentType: "text/xml",
   dataType: "xml",
   data: "<Person><FirstName>Nick</FirstName> <LastName>Riggs</LastName> <Age>30</Age></Person>",
   url: "Home/Create"
});

The response looks like:

<Person><Id>cbf6eedd-2147-46fc-925a-a570db7ab68a</Id> <FirstName>Nick</FirstName> <LastName>Riggs</LastName> <Age>30</Age></Person>

I hope the MVC API Action Filters helps the MVC community. It’s really helped clean up my controllers and create simple APIs for my AJAX calls and even external consumer applications.

Download MVC API Action Filter: http://mvcapi.codeplex.com/
Demonstration: http://examples.nickriggs.com/mvcapi/