public string PrepareAuthRequest(PrepareAuthenticationContext context) { var authorization = googleConsumer.ProcessUserAuthorization(); var callback = new Uri(Utils.GetUrlBase(context.Request) + context.RedirectPath); if (authorization == null) { return (googleConsumer .PrepareRequestUserAuthorization(returnTo: callback, scopes: new[] { "https://www.googleapis.com/auth/userinfo.profile" }) .Headers["Location"]); } return(null); }