Route not recognised in MVC 4 WebAPI - asp.net

Question

I haven't used the ASP.NET WebAPI much although I have used routes in straight MVC. Obviously I'm doing something wrong, perhaps someone can help?
I have one controller called UsersController and two methods on it, Register and Details, both take two string parameters and return a string, both marked as HttpGet.
Originally I started with two route mappings in WebApiConfig.cs:
config.Routes.MapHttpRoute(
name: "TestApi",
routeTemplate: "api/{controller}/{action}/{userId}/{key}"
);
config.Routes.MapHttpRoute(
name: "Test2Api",
routeTemplate: "api/{controller}/{action}/{userId}/{class}"
);
With this set up only the first route is found for a URL such as:
http://<domain>/api/users/register/a123/b456/
If I call:
http://<domain>/api/users/details/a123/b456/
I get a 404. If I swap the two routes around then I can call the Details method but not the Register method, again getting a 404. The workaround I have in place is to be more specific with the routes:
config.Routes.MapHttpRoute(
name: "TestApi",
routeTemplate: "api/{controller}/register/{userId}/{key}"
);
config.Routes.MapHttpRoute(
name: "Test2Api",
routeTemplate: "api/{controller}/details/{userId}/{class}/"
);
The UsersController looks like:
namespace HelloWebAPI.Controllers
{
using System;
using System.Web.Http;
using HelloWebAPI.Models;
public class UsersController : ApiController
{
[HttpGet]
public string Register(string userId, string key)
{
return userId + "-" + key;
}
[HttpGet]
public string Enrolments(string userId, string #class)
{
return userId + "-" + #class
}
}
}
So what I don't understand is why the {action} component of the route registered second is not being associated with the correct method.
Thanks
Joe

Answer 1

The routing in ASP.NET Web API works in three steps:
Matching the URI to a route template.
Selecting a controller.
Selecting an action.
The framework selects the first route in the route table that matches the URI, there is no "second guessing" in case when 2nd or 3rd step fails - just 404. In your case both URI are always matching the first route so the second is never used.
For further analysis let's assume that the first route is:
api/{controller}/{action}/{userId}/{key}
And you call it with following URI:
http://<domain>/api/users/enrolments/a123/b456/
In order to choose action framework is checking three things:
The HTTP method of the request.
The {action} placeholder in the route template, if present.
The parameters of the actions on the controller.
In this case the {action} part will be resolved correctly to enrolments, but framework will be looking for Enrolments method with userId and key parameters. Your method has a class parameter which is no match. This will result in 404.
To avoid the issue you have to make more specific routes (like you did) or unify parameters names.

Answer 2

You only need to define the one route:
config.Routes.MapHttpRoute(
name: "TestApi",
routeTemplate: "api/{controller}/{action}/{userId}/{key}"
);
Then change your controller methods to the following:
[HttpGet]
public string Register(string userId, string key)
{
return userId + "-" + key;
}
[HttpGet]
public string Details(string userId, string key)
{
return userId + "-" + key
}