title: Manually adding attribute to request body after authentication
body: <p>I am developing an ASP.NET Web API 2 application. When an HTTP request is going to come in which contains user authentication credentials, before it reaches the defined route(for which I am using Attribute routing), I want to somehow add a filter so that it can authenticate the user, and upon successful authentication, I want to fetch an ID from the repository and add it to the request body.</p>
  
  <p>Is it possible to add a filter before the request reaches the controller's action? And more importantly, is it possible to add some value to the request body after the authentication by the filter?</p>
  
  <p>Thanks.</p>