public static class RubberduckLocalization
{
    private static readonly Dictionary<LocalizationResource, object> localizationResources = new Dictionary<LocalizationResource, object>()
    {
        { LocalizationResource.RubberduckUI, new RubberduckUI() }
    };
    private static readonly Dictionary<LocalizationResource, ResourceDictionary> resourceDictionaries = new Dictionary<LocalizationResource, ResourceDictionary>();

    public static ResourceDictionary GetResourceDictionary(LocalizationResource translationResource)
    {
        Refresh(translationResource);
        return resourceDictionaries[translationResource];
    }

    public static void Refresh(LocalizationResource translationResource)
    {
        ResourceDictionary resourceDictionary;
        if (!resourceDictionaries.TryGetValue(translationResource, out resourceDictionary))
        {
            resourceDictionary = new ResourceDictionary();
            resourceDictionaries.Add(translationResource, resourceDictionary);
        }
        else
        {
            resourceDictionary.Clear();
        }
        object source = localizationResources[translationResource];
        foreach (PropertyInfo property in source.GetType().GetProperties(BindingFlags.Public | BindingFlags.Static))
        {
            if (property.PropertyType == typeof(string))
            {
                string name = property.Name;
                string value = (string)property.GetValue(source);
                resourceDictionary.Add("TEXT_" + name, value);
            }
        }
    }
}

public enum LocalizationResource
{
    RubberduckUI
}

// Example WPF GUI ctor
public InspectionResultsControl()
{
    InitializeComponent();

    Resources.MergedDictionaries.Add(RubberduckLocalization.GetResourceDictionary(LocalizationResource.RubberduckUI));

    _inspectionTypeGroupsViewSource = (CollectionViewSource)FindResource("InspectionTypeGroupViewSource");
    _inspectionTypeGroupsTemplate = (DataTemplate)FindResource("InspectionTypeGroupsTemplate");

    _moduleGroupsViewSource = (CollectionViewSource)FindResource("CodeModuleGroupViewSource");
    _moduleGroupsTemplate = (DataTemplate)FindResource("CodeModuleGroupsTemplate");

    Loaded += InspectionResultsControl_Loaded;
}

// Changes to App.cs
RubberduckUI.Culture = CultureInfo.GetCultureInfo(_config.UserSettings.LanguageSetting.Code);
RubberduckLocalization.Refresh(LocalizationResource.RubberduckUI);
_appMenus.Localize();