public static bool Login( string username, string password )
 {
     ATIdentity identity = ATIdentity.GetIdentity( username, password );
     if (identity.IsAuthenticated)
     {
         ATPrincipal principal = new ATPrincipal( identity );
         Csla.ApplicationContext.User = principal;
     }
     return identity.IsAuthenticated;
 }
 public static void Logout()
 {
     ATIdentity identity = ATIdentity.UnauthenticatedIdentity();
     ATPrincipal principal = new ATPrincipal( identity );
     Csla.ApplicationContext.User = principal;
 }