Cancel a user edit from property set in the ViewModel? - wpf

Question

quite a newbie question, i'm sure, but i wasn't able to find an answer...
I have a control (in this case- a combo box) which is bound to a ViewModel property:
<ComboBox
x:Name="methodTypeCmb"
Grid.Row="0" Grid.Column="2"
ItemsSource="{Binding Path=AllNames, Mode=OneTime}"
SelectedItem="{Binding Path=Name, ValidatesOnDataErrors=True, Mode=TwoWay}"
Validation.ErrorTemplate="{x:Null}"
/>
In my ViewModel, when this property changes, I want to ask the user to confirm the change.
If the user clicks 'no', I want to cancel the change.
However, I must be doing something wrong, because my view doesn't revert back to the previous value when the change is cancelled.
The ViewModel's property:
public string Name
{
get { return m_model.Name; }
set
{
if (MessageBox.Show("Are you absolutely sure?","Change ",MessageBoxButton.YesNo) == MessageBoxResult.Yes)
{
// change name
}
base.OnPropertyChanged("Name");
}
}

Answer 1

Because you are cancelling within the scope of the text changing event, wpf ignores the property changed event. You must call it from the dispatcher
Dispatcher.CurrentDispatcher.BeginInvoke((ThreadStart)delegate
{
OnPropertyChanged("Name");
});
You should leave your existing "OnPropertyChanged("Name");" at the bottom of the function just add the above line to the block where you are cancelling
EDIT: The following code works I have tested it
public string Newtext
{
get
{
return this._newtext;
}
set
{
if (MessageBox.Show("Apply?", "", MessageBoxButton.YesNo) == MessageBoxResult.Yes)
{
this._newtext = value;
this.OnPropertyChanged("Newtext"); //Ignored
}
else
{
Dispatcher.CurrentDispatcher.Invoke((ThreadStart)delegate
{
OnPropertyChanged("Newtext");
});
}
}
}