/// <summary>
/// Initializes the view and its data context.
/// </summary>
private void InitializePageState()
{
// Retrieve data from temporary storage if present;
// otherwise, copy data from CarDataStore.Car.
if (State.ContainsKey(CAR_INFO_KEY))
{
_car = (Car)State[CAR_INFO_KEY];
// Restore the read-only state of the odometer text box.
OdometerTextBox.IsReadOnly = (bool)State[ODOMETER_READONLY_STATE];
// Restore the change state except when the PhotoTask_Completed
// method has already set the change state.
if (!_hasUnsavedChanges)
{
_hasUnsavedChanges =
(bool)State[HAS_UNSAVED_CHANGES_KEY];
}
// Delete temporary storage to avoid unnecessary storage costs.
State.Clear();
}
else
{
_car = CarDataStore.Car;
// Delete the temporary photo if it exists. This prevents an old
// temporary photo selection from reappearing after tombstoning.
CarDataStore.DeleteTempCarPhoto();
// Disable the odometer text box when displaying a saved value.
OdometerTextBox.IsReadOnly = _car.InitialOdometerReading > 0;
// Disable the delete car button for new car
if (_car.InitialOdometerReading.Equals(0))
{
var deleteButton = (ApplicationBarIconButton)this.ApplicationBar.Buttons[1];
deleteButton.IsEnabled = false;
}
}
// Set the page data context to the car.
DataContext = _car;
}
/// <summary>
/// Displays a warning dialog box if the user presses the back button
/// and there are unsaved changes.
/// </summary>
/// <param name="e"></param>
protected override void OnBackKeyPress(
System.ComponentModel.CancelEventArgs e)
{
base.OnBackKeyPress(e);
// If there are no changes, do nothing.
if (!_hasUnsavedChanges)
{
return;
}
var result = MessageBox.Show("You are about to discard your " +
"changes. Continue?", "Warning", MessageBoxButton.OKCancel);
if (result == MessageBoxResult.OK)
{
CarDataStore.DeleteTempCarPhoto();
}
else
{
e.Cancel = true;
}
}