private void buttonList_Click(object sender, EventArgs e) //ok
        {
            Employee        emp   = new Employee();
            List <Employee> listE = emp.ListEmployees();

            listViewEmployee.Items.Clear();
            if (listE != null)
            {
                foreach (Employee current in listE)
                {
                    ListViewItem item = new ListViewItem(current.EmployeeId.ToString());
                    item.SubItems.Add(current.FirstName);
                    item.SubItems.Add(current.LastName);
                    item.SubItems.Add(current.JobTitle);
                    item.SubItems.Add(current.UserType);
                    item.SubItems.Add(current.Password);
                    item.SubItems.Add(current.Email);

                    listViewEmployee.Items.Add(item);
                }
            }
            else
            {
                MessageBox.Show("No data saved.");
            }
        }