private void AddSupervisorCommand(object model)
        {
            var supervisorModel = model as Supervisor;

            supervisorModel.SiteId      = SiteId;
            supervisorModel.CreatedDate = DateTime.Now;
            if (string.IsNullOrWhiteSpace(supervisorModel.SupervisorName))
            {
                NameVisibility = Visibility.Visible;
                return;
            }
            if (supervisorModel.MonthlySalary < 1)
            {
                SalaryVisibility = Visibility.Visible;
                return;
            }
            _repositoryManager.AddSupervisor(supervisorModel);
            Supervisors     = new ObservableCollection <Supervisor>(_repositoryManager.GetSupervisorsBySiteId(SiteId));
            SupervisorToAdd = new Supervisor();
        }