Web Api routes with controller and without controller in conjunction - asp.net-web-api

Question

I have two controllers.
one with classic REST functions.
public class ValuesController : ApiController
{
public IEnumerable<string> Get()
{
return new string[] { "value1", "value2" };
}
public string Get(int id)
{
return "value";
}
}
and one with custom function names with HttpAttributes
public class Values2Controller : ApiController
{
[HttpGet]
public IEnumerable<string> GetAll()
{
return new string[] { "value2_1", "value2_2" };
}
[HttpGet]
public string GetById(int id)
{
return "value " + id;
}
}
and I have my routes configured like this
config.Routes.MapHttpRoute(
name: "DefaultApi2",
routeTemplate: "api/{controller}/{action}/{id}",
defaults: new { id = RouteParameter.Optional }
);
config.Routes.MapHttpRoute(
name: "DefaultApi",
routeTemplate: "api/{controller}/{id}",
defaults: new { id = RouteParameter.Optional }
);
with this setting
http://localhost:xxxxx/api/Values2/1 does not get resolved
and if I put DefaultApi before DefaultApi2 then trying to access
http://localhost:xxxxx/api/Values2/GetAll
I get "The parameters dictionary contains a null entry for parameter 'id' "

Answer 1

The problem is that your route definitions are ambiguous. For example, for this URL:
http://localhost:xxxxx/api/Values2/1
the routing system can consider that the "1" segment is the action in the DefaultApi2 route, and the Id is null becasue you've defined it that way.
So, to break the ambiguity you need to use route constraints. This allows you to add rules to the different segments of your routes, so that they are not mismatched. Remember that the routes are eveluated in the order in which they are register.
So, for example, if you register first DefaultApi and then DefaultApi2, and you add a constraint which requires the Id for the first route to be numeric, both routes will work perfectly.
You could also add constraints on the controller name, or use a different prefix for each kind of controller for example api/ and api2/. The case is that the routes can be distinguished from each other.
Google "Web API route contraints", and you'll get info like this:
Creating a Route Constraint (C#)
The MSDN docs for RouteCollectionExtensions.MapHttpRoute Method (RouteCollection, String, String, Object, Object)are quite useless.