Commented Issue: Throw error message when users try to supply handlers(IRouteHandler or Message handlers) when using attribute routing [1428]

Handlers like IRouteHandler in MVC and HttpMessageHandler in Web API do not work with attribute routing. A user implementing IDirectRouteProvider might supply these handlers even though these handlers would never work. Instead of this we can throw an error message upfront when building the route table so that users know the issue rather than spending hours to detect this.
Comments: commit aa25b83909680094b75a58b316eed267dcf42c93