public override void Handle(ChangeMarkCommand command)
        {
            Mark mark = _dbContext.Marks.Find(command.Id);

            if (mark == null)
            {
                _result = new InvalidResult()
                          .WithError("No mark of this id has been found.");
            }

            mark.ChangeName(command.Name);
            mark.ChangeDescription(command.Description);

            _dbContext.Marks.Update(mark);
            _dbContext.SaveChanges();
            _result = new SuccessResult();
        }