I have a .NET 4.0 WPF application where the user can change the language (culture) 
I simply let the user select a language, create a corresponding CultureInfo and set:

```
Thread.CurrentThread.CurrentCulture = cultureInfo;
Thread.CurrentThread.CurrentUICulture = cultureInfo;

```

In the C# code this works fine. However in the WPF controls the culture is still en-US. This means for example that dates will be shown in the US format instead of whatever is correct for the current culture.

Apparently, this is not a bug. According to MSDN and several blog posts and articles on StackOverflow the WPF language does not automatically follow the current culture. It is en-US until you do this:

```
FrameworkElement.LanguageProperty.OverrideMetadata(
    typeof(FrameworkElement),
    new FrameworkPropertyMetadata(
        XmlLanguage.GetLanguage(CultureInfo.CurrentUICulture.IetfLanguageTag)));

```

See for example [StringFormat Localization issues in wpf](https://stackoverflow.com/questions/520115/stringfomat-localization-problem/520334#520334).

I do not completely understand what is going on here. It seems the Language property on all frameworkelements is set to the current culture. Anyway, it works. I do this when the application starts up and now all controls works as expected, and e.g. dates is formatted according to the current culture.

But now the problem: According to MSDN `FrameworkElement.LanguageProperty.OverrideMetadata` can only be called once. And indeed, if I call it again (when the user changes the language) it will throw an exception. So I haven't really solved my problem. 

The question: How can I reliably update the culture in WPF more than once and at any time in my applications life cycle?

(I found this when researching: <http://www.nbdtech.com/Blog/archive/2009/03/18/getting-a-wpf-application-to-pick-up-the-correct-regional.aspx>
and it seems he has something working there. However, I can't imagine how to do this in my application. It seems I would have to update the language in all open windows and controls and refresh all existing bindings etc.)