WPF TextBox SpellChecking Problem

How can I change the spellchecking language of a WPF textbox to french using XAML? I tried this but it doesn't work.

<TextBox AcceptsReturn="true" SpellCheck.IsEnabled="true" FontSize="12" BorderBrush="Blue" Height="100" Language="fr-fr" />

French is supposed to be one of the 4 supported languages for spellchecking in WPF so I don't understand why it doesn't work. I also 开发者_如何学运维tried fr-CA but it still won't work.

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You need resource file of .Net Framework for the language you want to activate…

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Try setting the XML language attribute. For me, this actually worked:

<TextBox AcceptsReturn="true" SpellCheck.IsEnabled="true" FontSize="12" BorderBrush="Blue" Height="100" xml:lang="fr" />