However, one thing you could try is put default strings into all XAML elements (TextBox, Label, TextBlock, etc.) and then replace them at runtime, for example in the Loaded event (or something that fires earlier.)

I think this way is way better than localization with Locbaml (at least for strings). The problem we have with Locbaml (as far as I tested) is that if a new localizable (e.g. Window) is added to your project AFTER localization process, you’ll need to regenerate the whole .csv file, so what will happen to all already localized content?

I’ve changed your code to contain fallback to default culture when a culture-specific resource is not found. Here it is :

public static ResourceDictionary LoadExternalResourceDictionary(string xamlFilename, CultureInfo culture)
{
string cultureName = string.Empty;

if (culture != null)
cultureName = string.Concat(”.”, culture.Name);

if(Path.HasExtension(xamlFilename))
{
string ext = Path.GetExtension(xamlFilename);
xamlFilename = xamlFilename.Remove(xamlFilename.Length - ext.Length);
}

try
{
string looseFile = string.Format(”pack://siteoforigin:,,,/{0}{1}.xaml”, xamlFilename, culture != null ? cultureName : string.Empty);
Uri uri = new Uri(looseFile, UriKind.Absolute);

System.Windows.Markup.XamlReader reader = new System.Windows.Markup.XamlReader();
System.Windows.Resources.StreamResourceInfo info = System.Windows.Application.GetRemoteStream(uri);

return reader.LoadAsync(info.Stream) as ResourceDictionary;
}
catch
{
if(culture != null)
{
return LoadExternalResourceDictionary(xamlFilename, null);
}
else
{
throw;
}
}
}