So I’ve got an existing ASP.NET MVC5 application and need to add a REST api using WebApi.

• Add a new Controller
• Select Web API 2 Controller – Empty (or whatever your preference is)
• Add you methods as normal
• Open Global.asax.cs and near the start, for example after AreaRegistration but before the route configuration, add

  GlobalConfiguration.Configure(WebApiConfig.Register);
  

easy enough. The key is to not put the GlobalConfiguration as the last line in the Global.asax.cs as I did initially.

If we assume your controller was named AlbumsController, it might looks something like this

public class AlbumsController : ApiController
{
   // api/albums
   public IEnumerable<Album> GetAllAlbums()
   {
      // assuming albums is populated 
      // with a list of Album objects
      return albums;
   }
}

as per the comment, access to the API will be through url/api/albums, see WebApiConfig in App_Start for the configuration of this URL.

In our controller we might have a method along the lines

public string Search(string criteria, bool ignoreCase = true)
{
   // do something useful
   return $"Criteria: {criteria}, Ignore Case: {ignoreCase}";
}

Note: I’ve not bothered using HttpUtility.HtmlEncode on the return string as I want to minimize the code for these snippets.

So we can simply create a query string as per

http://localhost:58277/Music/Search?criteria=something&ignoreCase=false

or we can add/change the routing in RouteConfig, so for example in RouteConfig, RegisterRoutes we add

routes.MapRoute(
   name: "Music",
   url: "{controller}/{action}/{criteria}/{ignoreCase}"
);

now we can compose a URL thus

http://localhost:58277/Music/Search/something/false

Note: the routing names /{criteria}/{ignoreCase} must have the same names as the method parameters.

Obviously this example is a little contrived as we probably wouldn’t want to create a route for such a specific method signature.

We might simply incorporate partial parameters into the routine, for example maybe all our MusicController methods took a citeria argument then we might use

routes.MapRoute(
   name: "Music",
   url: "{controller}/{action}/{criteria}"
);

Note: there cannot be another route with the same number of parameters in the url preceding this or it will not be used.

and hence our URL would like like

http://localhost:58277/Music/Search/something?ignoreCase=false