ComboBox validation error - why does it fail? - wpf

Question

The idea is simple: to select a period in seconds from a RibbonComboBox and save that to an app instance property. The underlying data is in milliseconds but the combo displays them in seconds.
The property in my app stores the time in millis:
private int _updatePeriod;
public int UpdatePeriod
{
get { return _updatePeriod; }
set
{
_updatePeriod = value;
InvokePropertyChanged(new PropertyChangedEventArgs("UpdatePeriod"));
}
}
in XAML i define a list of possible choices, in millis like this:
<x:Array x:Key="UpdateFrequenciesCollection" Type="{x:Type System:Int32}" >
<System:Int32 >100</System:Int32>
<System:Int32 >200</System:Int32>
<System:Int32 >500</System:Int32>
<System:Int32 >1000</System:Int32>
<System:Int32 >2000</System:Int32>
</x:Array >
I then have a ribbon toolbar combo box setup like this:
<ribbon:RibbonComboBox IsEditable="False" AllowDrop="False" Grid.Column="1" Grid.Row="1" IsDropDownOpen="False">
<ribbon:RibbonGallery x:Name="RibbonGalleryUpdatePeriod" SelectedValue="{Binding Path=UpdatePeriod, Mode=TwoWay, Source={x:Static Application.Current}}">
<ribbon:RibbonGalleryCategory x:Name="RibbonGalleryCategoryUpdatePeriod" ItemTemplate="{StaticResource UpdatePeriodTemplate}" ItemsSource="{Binding Source={StaticResource UpdateFrequenciesCollection}}">
</ribbon:RibbonGalleryCategory>
</ribbon:RibbonGallery>
</ribbon:RibbonComboBox>
This is the simple template for the combo box item:
<DataTemplate x:Key="UpdatePeriodTemplate">
<StackPanel Orientation="Horizontal" >
<TextBlock Text="{Binding Converter={StaticResource DivideConverter}, ConverterParameter=1000, StringFormat={}{0:0.0 s}}"/>
</StackPanel>
</DataTemplate>
Functionally its okay, as in it sets and get the correct value in the combobox<->UpdatePeriod. However the dropdown always has a red border which I think indicates an a validation error. Any idea what can cause this, or how I can debug the error in some way?? Much appreciated!

Answer 1

If your Binding has associated validation rules but you do not specify an ErrorTemplate on the bound control, a default ErrorTemplate will be used to notify users when there is a validation error. The default ErrorTemplate is a control template that defines a red border in the adorner layer.
I guess RibbonComboBox does define a validation rule.
You can set the attached property PresentationTraceSources.TraceLevel and see the binding error but I would start with Snoop