In App.xaml add key which points to your class LocalizedStrings:
<Application.Resources xmlns:my="clr-namespace:NameSpaceWhereLocalizedStrings">
<my:LocalizedStrings x:Key="Localized"/>
</Application.Resources>
clr-namespace: - is a namespace where you have your LocalizedStrings (probably your main namespace). Then you can use in any other xaml file your LocalizedResources:
<TextBlock Text="{Binding LocalizedResources.Hallo, Source={StaticResource Localized}}"/>
Hallo - is your variable in AppResources.resx (of course check if it's public). LocalizedResources is a class which you probably have as a default in LocalizedStrings.cs:
public class LocalizedStrings
{
private static AppResources _localizedResources = new AppResources();
public AppResources LocalizedResources { get { return _localizedResources; } }
}
In code I'm using then:
string myName = AppResources.Hallo;
Note that after adding a variable or changing it you will have to rebuild the project.