Items in listview not sorted correctly

Question

I have a listview which I reorder by clicking on the gridViewheader. There is one problem though and it is  that our swedish accented characters (for example "ä" which is a with two dots over). For some reason they are sorted like an unaccented character.

I have tried to set the Items.Culture = Thread.CurrentThread.CurrentCulture;

have also tried to set the default language/culture by doing this in my App.XAML.cs:

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

This works when for example using converters (without this code I would get the defualt us culture). But it does not help with sorting the listview (a nd Items.Culture is null.

Any ideas?