Question

Imagine a system with Users, Groups with corresponding ApiControllers.
Then imagine following access patterns:

/api/users                  
/api/users/1
/api/users?groupId=1    <- #1 returns users belonging to group id 1 via Get(int? groupId)

/api/groups/
/api/groups/1
/api/groups/1/users     <- #2 sub resource, returns users belonging to group id 1

Is it possible to delegate responsibility of #2 to #1’s Get(int? groupId) method?
I’d like to keep responsibility of handling sub-resources with their original Controller.
In another words, If a sub-resource also exists as resource then sub-resource handling should be? delegated to primary resource controller…

P.S.
Now, I am not sure if the above approach is “cosher” with RESTfull styles, that is whole other discussion…

Answer 1

WEB Api Beta isn’t supporting method level attribute for routing. They said, that are thinking of improving the routing story for the next release.

For now the only way (as i know) is to map explicitly those routes. In your case:

 // for your rest style api 
 routes.MapHttpRoute(
     name: "UserGroups",
     routeTemplate: "api/groups/{groupID}/users",
     defaults: new { controller = "Users"},
     constraints: new { groupID = @"\d+" } 
 );

and for RPC URI style the default route will work as glance.

 routes.MapHttpRoute(
           name: "ApiDefault",
           routeTemplate: "api/{controller}/{id}",
           defaults: new { controller = "Users", id = RouteParameter.Optional }
       );

And also you can override DefaultHttpControllerFactory class to create in your way instances of controllers.

Hope this help.