public FrmMain()
 {
     InitializeComponent();
     try
     {
         ClsVehicleBusiness.Retrieve();
     }
     catch (Exception ex)
     {
         MessageBox.Show(ex.Message);
     };
 }
 private void btnClose_Click(object sender, EventArgs e)
 {
     try
     {
         ClsVehicleBusiness.Save();
     }
     catch (Exception ex)
     {
         MessageBox.Show(ex.Message);
     }
     Close();
 }
 private void updateDisplay()
 {
     lblTotalCashflowAmount.Text = string.Format("{1:C}", ClsVehicleBusiness.VehicleList.Count, ClsVehicleBusiness.TotalCashflow());
     lstLicencePlates.DataSource = null;
     lstLicencePlates.DataSource = ClsVehicleBusiness.VehicleList.Values.ToList <ClsVehicle>();
 }