Web API in MVC solution in separate project

Filip W

Unfortunately you are wrong about that - I am presuming that I can share all my attributes etc between web api and mvc controllers so on the face it, it does not seem a massive change for me.

Many of the concepts used by Web API and MVC, even though similar at first glance, are actually not compatible. For example, Web API attributes are System.Web.Http.Filters.Filter and MVC attributes are System.Web.Mvc.Filter - and they are not interchangeable.

Same applies to many other concepts - model binding (completely different mechanisms), routes (Web API uses HTTPRoutes not Routes, even though they both operate on the same underlying RouteTable), dependency resolver (not compatible) and more - even though similar on the surface, are very different in practice. Moreover, Web API does not have a concept of areas.

Ultimately, if all you are trying to do achieve is to have a "new, trendy" way of serving up JSON content - think twice before going down that path. I certainly wouldn't recommend refactoring any existing code unless you are really looking into embracing HTTP and building your app in a RESTful way.

It all really depends on what you are building. If you are starting a new project, and all you need is to serve up some JSON to facilitate your web app - provided you willing to live with some potentially duplicate code (like the stuff I mentioned above), Web API could easily be hosted within the same project as ASP.NET MVC.

I would only separate Web API into a separate project if you are going to build a proper API for your online service - perhaps to be consumed by external customers, or by various devices - such as fueling your mobile apps.

David Peden

IMO, security and deployment should drive your decision. E.g., if your MVC app uses Forms authentication but you're interested in using Basic authentication (with SSL) for your API, separate projects are going to make your life easier. If you want to host yout site at www.example.com but host your API as api.example.com (vs. www.example.com/api), separate projects will make your life easier. If you separate your projects and subdomain them accordingly and you intend to leverage your own API from your MVC app, you will have to figure out how to deal with the Same Origin Policy issue for client-side calls to your API. Common solutions to this are to leverage jsonp or CORS (preferably if you can).

Update (3/26/2013): Official CORS support is coming: http://aspnetwebstack.codeplex.com/wikipage?title=CORS%20support%20for%20ASP.NET%20Web%20API


After some degree of experience (creating API for apps and for mvc). I mostly do both.

I create a separate project for api calls that come from other clients or other devices (Android/IOS apps). One of the reasons is because the authentication is different, it is token based (to keep it stateless). I do not want to mix this within my MVC application.

For my javascript/jquery api calls to my mvc application, I like to keep things simple so I include a web api inside my MVC application. I do not intend to have token based authentication with my javascript api calls, because hey, it's in the same application. I can just use [authorize] attribute on a API endpoint, when a user is not logged in, he will not get the data.

Furthermore, when dealing with shopping carts and you want to store a users shopping cart in a session (while not logged in), you need to have this in your API as well if you add/delete products via your javascript code. This will make your API stateful for sure, but will also reduce the complexity in your MVC-API.

Jeroen K

Steven from SimpleInjector (IoC framework) advises two separate projects: What is the difference between DependencyResolver.SetResolver and HttpConfiguration.DependencyResolver in WebAPI

I have recently done almost the same thing: I started with a new MVC 4 web application project choosing the Web API template in VS2012.

This will create a Web API hosted in the same application as MVC.

I wanted to move the ApiControllers into a separate class library project. This was fairly easy but the solution was a bit hidden.

In AssemblyInfo.cs of the MVC 4 project add similar line of code

[assembly: PreApplicationStartMethod(typeof(LibraryRegistrator), "Register")]

Now you need the class LibraryRegistrator (feel free to name it whatever)

public class LibraryRegistrator
        public static void Register()

In the MVC 4 project also add reference to the Api library.

Now you can add Api controllers to your own separate class library (yourown.dll).

Even if your project is so complex as to warrant two "front ends" then I would still only consider splitting out webapi into a separate project as a last resort. You will have deployment headaches and it would be difficult for a newbie to understand the structure of your solution. Not to mention routing issues.

I would aim to keep the system.web namespace isolated in the one "presentation layer". Despite the webapi not being presentational it is still part of the interface of your application. As long as you keep the logic in your domain and not your controllers you should not run into too many problems. Also, don't forget to make use of Areas.

In addition to setup the separate DLL for the Web.Api.

Just a Suggestion:

  1. Create the Project
  2. Nugget WebActivatorEx
  3. Create a a class Method to be called upon app_start

    [assembly: WebActivatorEx.PostApplicationStartMethod(typeof(API.AppWebActivator),"Start")]

    [assembly:WebActivatorEx.ApplicationShutdownMethod(typeof(API.AppWebActivator), "Shutdown")]

  4. Register a web.api routes inside the Start Method

    public static void Start() { GlobalConfiguration.Configure(WebApiConfig.Register); }

  5. Reference the Project to the Web Project. to activate the Start Method.

Hope this helps.

I tried to split the API controllers into a new project. All I've done is to create a new library project, moved the controllers inside folder named API. Then added the reference of the library project to the MVC project.

The webAPI configuration is left in the MVC project itself. It works fine.