public override bool IsUserInRole(string username, string roleName)
        {
            using (var db=new VehiculosLuisEntities())
               {

               try
               {
                   var us = db.UsuarioSet.First(o => o.Login == username);
                   return us.Rol.Nombre == roleName;
               }
               catch (Exception e)
               {
                   return false;
               }
               }
        }
        public override string[] GetRolesForUser(string username)
        {
            using (var db = new VehiculosLuisEntities())
            {

                try
                {
                    var us = db.UsuarioSet.First(o => o.Login == username);
                    return new []{ us.Rol.Nombre};
                }
                catch (Exception e)
                {
                    return null;
                }
            }
        }
        public override bool ValidateUser(string username, string password)
        {
            using (var db=new VehiculosLuisEntities())
               {

               var p = SeguridadUtilidades.GetSha1(password);
            return db.UsuarioSet.Any(o => o.Password == p &&
                                    o.Login==username);
            }
        }
        public override MembershipUser GetUser(string username, bool userIsOnline)
        {
            using (var db = new VehiculosLuisEntities())
            {

                var user= db.UsuarioSet.FirstOrDefault(o => o.Login ==
                                                username );
                if (user == null)
                    return null;

                return new UsuarioMembership(user);
            }
        }