Custom authentication handler when using MapHttpAttributeRoutes in Web API 2 - vb.net

Question

In a Web API 2 web service I currently have a custom authentication handler set up for the default route in WebApiConfig.vb, the default route looks like this:
config.Routes.MapHttpRoute(
name:="DefaultApi",
routeTemplate:="api/{controller}/{id}",
defaults:=New With {.id = RouteParameter.Optional},
constraints:=Nothing,
handler:=New AuthenticationHandler() With {.InnerHandler = New Dispatcher.HttpControllerDispatcher(config)}
)
And the AuthenticationHandler class looks like this:
Imports System.Net
Imports System.Net.Http
Imports System.Threading.Tasks
Imports System.Runtime.Caching
Imports System.Text
Imports System.Security.Cryptography
Public Class AuthenticationHandler
Inherits DelegatingHandler
Protected Overrides Function SendAsync(request As HttpRequestMessage, cancellationToken As Threading.CancellationToken) As Threading.Tasks.Task(Of HttpResponseMessage)
Dim response As New HttpResponseMessage
Dim lblnIsAuthenticated As Boolean = False
Dim tsc As New TaskCompletionSource(Of HttpResponseMessage)
'// Do the authentication work here...
if not lblnIsAuthenticated then
'// Set the response
response.StatusCode = HttpStatusCode.BadRequest
response.Headers.Add("Status-Message", "Authentication failed.")
tsc.SetResult(response)
Return tsc.Task
end if
Return MyBase.SendAsync(request, cancellationToken)
End Function
When I upgraded this service to Web API 2 I wanted to take advantage of http attribute routing, so I added config.MapHttpAttributeRoutes() to WebApiConfig.vb and set up some of the controllers to use the Route and RoutePrefix attributes. The problem is that this routing method doesn't take advantage of the custom authentication handler. Is there any way to implement this same authentication handler for the http attribute routing? I've searched around for a solution to this but don't see how to make this work. Or do I need to just do standard routes?
UPDATE --
I also have some other routes in WebApiConfig.vb that have a different authentication handler on them so I don't think I can apply one handler globally.

Answer 1

You should be able to add your handler to GlobalConfiguration.Configuration.MessageHandlers; unless I'm mistaken the handlers added there are always invoked for all the requests. Unless you're trying to do something different?