Custom method names in ASP.NET Web API

By default the route configuration follows RESTFul conventions meaning that it will accept only the Get, Post, Put and Delete action names (look at the route in global.asax => by default it doesn't allow you to specify any action name => it uses the HTTP verb to dispatch). So when you send a GET request to /api/users/authenticate you are basically calling the Get(int id) action and passing id=authenticate which obviously crashes because your Get action expects an integer.

If you want to have different action names than the standard ones you could modify your route definition in global.asax:

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

Now you can navigate to /api/users/getauthenticate to authenticate the user.

This is the best method I have come up with so far to incorporate extra GET methods while supporting the normal REST methods as well. Add the following routes to your WebApiConfig:

routes.MapHttpRoute("DefaultApiWithId", "Api/{controller}/{id}", new { id = RouteParameter.Optional }, new { id = @"\d+" });
routes.MapHttpRoute("DefaultApiWithAction", "Api/{controller}/{action}");
routes.MapHttpRoute("DefaultApiGet", "Api/{controller}", new { action = "Get" }, new { httpMethod = new HttpMethodConstraint(HttpMethod.Get) });
routes.MapHttpRoute("DefaultApiPost", "Api/{controller}", new {action = "Post"}, new {httpMethod = new HttpMethodConstraint(HttpMethod.Post)});

I verified this solution with the test class below. I was able to successfully hit each method in my controller below:

public class TestController : ApiController
{
    public string Get()
    {
        return string.Empty;
    }

    public string Get(int id)
    {
        return string.Empty;
    }

    public string GetAll()
    {
        return string.Empty;
    }

    public void Post([FromBody]string value)
    {
    }

    public void Put(int id, [FromBody]string value)
    {
    }

    public void Delete(int id)
    {
    }
}

I verified that it supports the following requests:

GET /Test
GET /Test/1
GET /Test/GetAll
POST /Test
PUT /Test/1
DELETE /Test/1

Note That if your extra GET actions do not begin with 'Get' you may want to add an HttpGet attribute to the method.