public ServiceResponse <List <MailEntity> > ListUnreadMails(int toUserId) { var serviceResponseBuilder = new ServiceResponseBuilder <List <MailEntity> >(); var obj = _repository.ListUnreadMails(toUserId); if (obj == null) { return(serviceResponseBuilder.NotOk(new ServiceError() { Code = "200002", Message = "Unread mails can not list.", InnerMessage = "Unread mails can not list." })); } return(serviceResponseBuilder.Ok(obj)); }