Put this code in your application startup.
Private Sub Application_Startup(ByVal sender As Object, ByVal e As System.Windows.StartupEventArgs) Handles Me.Startup
Dim objCulture As CultureInfo = New CultureInfo("en-US")
Thread.CurrentThread.CurrentCulture = objCulture
Thread.CurrentThread.CurrentUICulture = objCulture
'HACK - Ensure the current culture passed into bindings is the OS culture.
' By default, WPF uses en-US as the culture, regardless of the system settings.
FrameworkElement.LanguageProperty.OverrideMetadata(
GetType(FrameworkElement), New FrameworkPropertyMetadata(System.Windows.Markup.XmlLanguage.GetLanguage(CultureInfo.CurrentCulture.IetfLanguageTag)))
End Sub
Cheers, Karl - Microsoft Product Team, Code Project MVP - http://karlshifflett.wordpress.com/