ASP.NET WebApi - Multiple GET actions in one controller

Question

I have Users controller and basic REST pattern is working just fine. However I need one additional pattern users/{id}/usergroups that will return all user groups for that user.

What would be the best way to implement this since I imagine I will need similar routes on many more controllers. Just default ones are not enough...

Error

Multiple actions were found that match the request: Api.Models.Users.User GetUser(Int32) on type Api.Controllers.UsersController System.Collections.Generic.IEnumerable`1[Api.Models.Users.UserGroup] GetUserGroups(Int32) on type Api.Controllers.UsersController

Code

// GET api/Users
public IEnumerable<User> GetUsers()

// GET api/Users/5
public User GetUser(int id) // THIS IS CONFLICT 1

// PUT api/Users/5
public HttpResponseMessage PutUser(int id, User user)

// POST api/Users
public HttpResponseMessage PostUser(User user)

// DELETE api/Users/5
public HttpResponseMessage DeleteUser(int id)

// GET api/Users/5/UserGroups
public IEnumerable<UserGroup> GetUserGroups(int id)  // THIS IS CONFLICT 2

Edit 1

I did what amhed suggested and it doesn't solve the issue.

// GET api/Users/5
[HttpGet, ActionName("getuser")]
public User GetUser(int id) // THIS STILL DOES NOT WORK

// GET api/Users/5/UserGroups
[HttpGet, ActionName("usergroups")]
public IEnumerable<UserGroup> GetUserGroups(int id) // THIS WORKS

// ROUTES
config.Routes.MapHttpRoute(
    name: "DefaultApi",
    routeTemplate: "{controller}/{id}/{action}",
    defaults: new { id = RouteParameter.Optional, action = RouteParameter.Optional }
);

Answer 1

You can either: just define one Get method, and have an optional Id Parameter like this:

public IEnumerable<User> GetUsers(int? id){
    if (id.HasValue)
    {
         //return collection of one item here
    }
    //return collection of all items here
}

Or you can have multiple Gets decorated with the ActionName Attribute

// GET api/Users
[ActionName("GetAll")]
public IEnumerable<User> GetUsers()

// GET api/Users/5
[ActionName("Get")]
public User GetUser(int id) // THIS IS NO LONGER IN CONFLICT

And then define the routes on your RouteConfig like so:

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

Answer 2

I'm stuck using Web API v1 and came up w/ the following solution to this. For all of your general routes, declare the ActionName as "Default". Then in your route config, set the default action="Default". This changes your call to /Users/5 to users/5/default and ensures it maps to the right place. The only problem I've found w/ this solution is that the documentation will show the /Default part of the route. It looks like you can edit your view to exclude these as this guy did (https://stackoverflow.com/a/29353198/4374666).

If you're using v2, it seems like Attribute Routing would be the cleanest way.

// GET api/Users/5
[HttpGet, ActionName("Default")]
public User GetUser(int id) // THIS STILL DOES NOT WORK

// GET api/Users/5/UserGroups
[HttpGet, ActionName("usergroups")]
public IEnumerable<UserGroup> GetUserGroups(int id) // THIS WORKS

// ROUTES
config.Routes.MapHttpRoute(
name: "DefaultApi",
routeTemplate: "{controller}/{id}/{action}",
    defaults: new { id = RouteParameter.Optional,
 action = "Default" }
);