Web API: How to get a route parameter when controller action does not have corresponding argument

Question

We build multi-tenancy application with Web API 2. We want to embed tenant info into the URL so that every request can get it. Eg http://localhost/tenant1/api/test . We added an action filter that should extract tenant from the request. However, it works only when controller action method signature has corresponding parameter.

Here is the code:

public class ValidationFilter : ActionFilterAttribute
{
    public override Task OnActionExecutingAsync(HttpActionContext actionContext, CancellationToken cancellationToken)
    {
        // works only if controller action has that argument
        var tenant = actionContext.ActionArguments["tenant"]; 

        Console.Out.WriteLine("tenant = {0}", tenant);
        return base.OnActionExecutingAsync(actionContext, cancellationToken);
    }
}

It works well when controller is like that:

[RoutePrefix("{tenant}")]
public class TestController : ApiController
{
    [Route("api/test")]
    public string Get(string tenant) // we don't need it here
    {
        return "hello";
    }
}

The tenant is going to be used only in action filter, so adding it to each and every controller method seems to be a silly thing. We want that controller to be:

 public string Get() {...}

Is there any way to obtain that value in action filter when controller action does not have a corresponding argument?

Answer 1

Found answer just after posting the question :)

  actionContext.ControllerContext.RouteData.Values["tenant"]

just works even when action does not have that argument.