public virtual void AddRole(Role role)
 {
     if (!_roles.Contains(role))
     {
         _roles.Add(role);
     }
 }
        public void Seed()
        {
            var role = new Role
                           {
                               Name = "Admin"
                           };

            var role2 = new Role
                            {
                                Name = "User"
                            };

            _session.Save(role);
            _session.Save(role2);
        }