public ActionResult DeleteForm(UserGroup userGroup)
        {
            Require.NotNull(userGroup, nameof(userGroup));
            UserGroupDeleteViewModel userGroupDeleteViewModel = new UserGroupDeleteViewModel(userGroup);

            if (UserGroupService.AreUsersAssigned(userGroup))
            {
                return(View("CanNotDelete", userGroupDeleteViewModel));
            }
            return(View("Delete", userGroupDeleteViewModel));
        }