private void LoadListBoxCreatedVehicles()
        {
            Fahrzeugtyp aVehicleType = (Fahrzeugtyp)comboBoxVehicleType.SelectedItem;

            if (aVehicleType != null)
            {
                list.VehicleSortedByTypeList.Clear();
                listBoxVehicleInformation.Items.Clear();
                foreach (Fahrzeug vehicle in list.VehicleList)
                {
                    if (aVehicleType.Equals(vehicle.Fahrzeugtyp) && vehicle.Verfügbar)
                    {
                        list.addToVehicleSortedByTypeList(vehicle);
                    }
                }

                if (list.VehicleSortedByTypeList.Count != 0)
                {
                    foreach (Fahrzeug vehicle in list.VehicleSortedByTypeList)
                    {
                        listBoxVehicleInformation.Items.Add(vehicle);
                    }

                    EnableOrderComponents(true);
                    listBoxVehicleInformation.SelectedIndex = 0;
                }
                else
                {
                    MessageBox.Show("Für diesen Fahrzeugtyp sind momentan keine Fahrzeuge verfügbar.");
                    listBoxVehicleInformation.Items.Clear();
                    EnableOrderComponents(false);
                }
            }
        }
        private void LoadListBoxCreatedVehicles()
        {
            Fahrzeugtyp aVehicleType = (Fahrzeugtyp)comboBoxVehicleType.SelectedItem;

            if (aVehicleType != null)
            {
                list.VehicleSortedByTypeList.Clear();
                listBoxCreatedVehicles.Items.Clear();
                foreach (Fahrzeug vehicle in list.VehicleList)
                {
                    if (aVehicleType.Equals(vehicle.Fahrzeugtyp))
                    {
                        list.addToVehicleSortedByTypeList(vehicle);
                    }
                }

                foreach (Fahrzeug vehicle in list.VehicleSortedByTypeList)
                {
                    listBoxCreatedVehicles.Items.Add(vehicle);
                }

                if (!buttonCreateVehicle.IsEnabled)
                {
                    listBoxCreatedVehicles.SelectedIndex = 0;
                }
            }
        }