public IHttpActionResult PutEmail([FromUri] Guid id, [FromBody] string email)
        {
            TeacherDto teacher = db.ChangeEmail(id, email);

            try
            {
                teacher = db.ChangeEmail(id, email);
            }
            catch (NullReferenceException e)
            {
                logger.Error(e.Message);
                return(NotFound());
            }
            return(Ok(teacher));
        }