title: Authenticate User using Windows Authentication in REST WCF Web API
body: <p>I have a requirement to expose some WCF Web API to a 3rd party system. The 3rd party system may validate the users using Windows Authentication.  My Web service will expose a Login method where the username is passed in.  I need to authenticate the passed in user using Windows Authentication.  </p>
  
  <p>I try to determine the role for the user by using:</p>
  
  <pre><code> Roles.GetRolesForUser(UserID)
  </code></pre>
  
  <p>I get the following error message:
  "Method is only supported if the user name parameter matches the user name in the current Windows Identity. "</p>
  
  <p>How do I validate a passed in username using Windows Authentication?</p>