public Operation <StaffModel> CreateStaff(StaffModel model)
        {
            return(System.Operation.Create(() =>
            {
                try
                {
                    var isExists = _context.Staffs.Where(c => c.Name == model.Name /*c.StaffName == model.StaffName &&*//* c.StaffNo == model.StaffNo*/).FirstOrDefault();
                    if (isExists != null)
                    {
                        throw new Exception("user email already exist");
                    }

                    //var exist = _context.Staffs.Where(e => e.StaffNo == model.StaffNo).FirstOrDefault();
                    //if (exist != null) throw new Exception("user staffno already exist");

                    var entity = model.Create(model);
                    _context.Staffs.Add(entity);
                    _context.SaveChanges();
                }
                catch (Exception xe)
                {
                    throw xe;
                }
                //model.Validate();

                return model;
            }));
        }