Silverlight AutoCompleteBox NotifyPropertyChanged does not update screen - silverlight

Question

It seems a few people are having problems with updating text AutoCompleteBox in Silverlight and sadly I've joined the ranks.
I've an derived class called EditableCombo like this;
public class EditableCombo : AutoCompleteBox
{
ToggleButton _toggle;
Path _btnPath;
TextBox _textBox;
...animation and toggle button stuff...
public override void OnApplyTemplate()
{
...animation and toggle button stuff...
//required to overcome issue in AutoCompleteBox that prevents the text being updated in some instances
//http://stackoverflow.com/questions/8488968/silverlight-5-autocompletebox-bug?rq=1
_textBox = GetTemplateChild("Text") as TextBox;
if (_textBox == null)
throw new NullReferenceException();
if (_textBox != null)
_textBox.TextChanged += TextBoxChanged;
base.OnApplyTemplate();
}
void TextBoxChanged(object sender, TextChangedEventArgs e)
{
Debug.WriteLine("text box changed fired new value: " + _textBox.Text);
Text = _textBox.Text;
OnTextChanged(new RoutedEventArgs());
}
...animation and toggle button stuff...
}
that enables users to click a togglebutton and select from the drop down list to choose an option or type in a new value like a standard combobox control.
My view has an EditableCombo control bound to a viewmodel containing a Gender property;
public string Gender
{
get
{
Debug.WriteLine("Gender get executed - Model.Gender = " + Model.Gender);
return Model.Gender;
}
set
{
if (Model.Gender == value) return;
MonitoredNotificationObject.RaisePropertyChanged(() => Model.Gender, value, this, true);
}
}
My viewmodel uses a MonitoredNotificationObject to maintain a undo/redo history and notify of any property changes;
public void RaisePropertyChanged(Expression<Func<string>> propertyExpression,
string newValue,
object sender,
bool canChain)
{
PropertyExpressionHelper propertyExpressionHelper = new PropertyExpressionHelper(propertyExpression)
{
NewValue = newValue
};
#if DEBUG
VerifyPropertyExists(propertyExpressionHelper.Name, sender);
#endif
var monitoredAction = new MonitoredProperty<TViewModel, TModel>(this)
{
ObjectPropertyName = propertyExpressionHelper.MakeObjectPropertyName(),
PropertyExpressionHelper = propertyExpressionHelper,
Sender = (TViewModel) sender,
CanChain = canChain
};
propertyExpressionHelper.SetToNewValue();
RaisePropertyChanged(propertyExpressionHelper.Name, sender);
MaintainMonitorState(monitoredAction);
}
Undo and redo are implemented as below (undo shown);
public override bool UndoExecute(MonitoredObject<TViewModel, TModel> undoAction,
Stack<MonitoredObject<TViewModel, TModel>> redoActions,
Stack<MonitoredObject<TViewModel, TModel>> undoActions)
{
PropertyExpressionHelper.SetToNewValue();
redoActions.Push(undoAction);
var action = (MonitoredProperty<TViewModel, TModel>) undoAction;
HandleAutoInvokedProperties(action);
if (action.CanChain)
{
if (undoActions.Any())
{
if (CanDoChain(undoActions, action))
return true;
}
}
action.RaiseChange();
Sender.RaiseCanExecuteChanges();
return false;
}
The property change notification is raised like this;
protected virtual void RaiseChange()
{
MonitoredNotificationObject.RaisePropertyChanged(PropertyExpressionHelper.Name, Sender);
if (RaiseChangeAction != null)
RaiseChangeAction.Invoke();
}
Using the above works fine for normal textboxes and successfully allows the user to undo and redo their changes as they desire. This also works for the EditableCombo when the user types an entry in the field - again, undo and redo perform as expected.
The issue is when the user selects a new value in the EditableCombo from the drop down list. The field updates, the Gender is set and everything looks fine. Clicking Undo successfully changes the field back to its original value - everything looking dandy.
However, when the user tries to redo the change the on screen value does not update. The underlying value is changed, the get on the Gender property is called and the Model.Gender value is correctly set. But then nothing. The screen does not update. The editablecombo control TextBoxChangedEvent does not fire so unsurprisingly the value on screen is not correct.
Basically the control is not being notified of the change.
Any ideas?
Update:
The view containing the EditableCombo has a viewmodel containing the Gender property. The property is bound like this;
<EditCombo:EditableCombo ItemsSource="{Binding Genders}"
ItemTemplate="{StaticResource editableComboDataTemplate}"
Style="{StaticResource EditableComboStyle}"
Text="{Binding Path=Gender,
UpdateSourceTrigger=PropertyChanged,
Mode=TwoWay,
ValidatesOnDataErrors=True}"
TextBoxStyle="{StaticResource editableComboDataEntryField}"
ValueMemberPath="Value" />
My implementation of undo/redo works fine for non-editablecombo controls and for the editablecombo when the new values are entered via the keyboard. The redo problem is only apparent when a property has been changed via the drop down toggle button. I know the underlying values are correctly updated as explained previously (and also, for example, as ValidatesOnDataErrors is on, when I redo and set the Gender property back to a valid value the red border signifying an error disappears - BUT, the text remains unchanged).
For whatever reason, the TextBoxChanged event never fires in the above scenario. Could it be the event is being handled elsewhere?

Answer 1

Does it work if you add this line:
Model.Gender = value;
to the property setter?