WebAPI - How to get UserID from token

I have WebApi application and added UserID to token in ApplicationOAuthProvider class:

    public override Task TokenEndpoint(OAuthTokenEndpointContext context)
    {
        foreach (KeyValuePair<string, string> property in context.Properties.Dictionary)
        {
            context.AdditionalResponseParameters.Add(property.Key, property.Value);
        }

        context.AdditionalResponseParameters.Add("ID", context.Identity.GetUserId<int>());

        return Task.FromResult<object>(null);
    }

Now how can I get this ID in my controller method?

I try the following:

[Authorize]
public class ApiEditorialController : ApiController
{

    public HttpResponseMessage GetEditorialRequests()
    {
        int id = HttpContext.Current.User.Identity.GetUserId<int>();

        var r = Request.CreateResponse(HttpStatusCode.Accepted);
        r.ReasonPhrase = "Cool!";
        return r;
    }

}

But I get NullReferenceException on

int id = HttpContext.Current.User.Identity.GetUserId<int>(); 

string....

UPDATE: Look at the Response below (from Francis Ducharme) just override OnAuthorization instead on create private contructor :)

public class AuthorizeApiFilter : AuthorizeAttribute
{
    public override void OnAuthorization(HttpActionContext actionContext)
    {
        string token = string.Empty;
        AuthenticationTicket ticket;

        token = (actionContext.Request.Headers.Any(x => x.Key == "Authorization")) ? actionContext.Request.Headers.Where(x => x.Key == "Authorization").FirstOrDefault().Value.SingleOrDefault().Replace("Bearer ", "") : "";

        if (token == string.Empty)
        {
            actionContext.Response = actionContext.Request.CreateResponse(HttpStatusCode.Unauthorized, "Missing 'Authorization' header. Access denied.");
            return;
        }

        //your OAuth startup class may be called something else...
        ticket = Startup.OAuthOptions.AccessTokenFormat.Unprotect(token);

        if (ticket == null)
        {
            actionContext.Response = actionContext.Request.CreateResponse(HttpStatusCode.BadRequest, "Invalid token decrypted.");
            return;
        }

        // you could perform some logic on the ticket here...

        // you will be able to retrieve the ticket in all controllers by querying properties and looking for "Ticket"... 
        actionContext.Request.Properties.Add(new KeyValuePair<string, object>("Ticket", ticket));
        base.OnAuthorization(actionContext);
    }
}

Thank you, Francis Ducharme