How to embed multilanguage *.resx (or *.resources) files in single EXE?

My solution: program contains only one default language resource file (resx). All other languages are compiled from .resx to .resources and embedded as resource file. Important! I have changed extension because ".resources" is recognized as a special type of resource, so my French files is named "PIAE.LangResources.fr".

Here is simple code to retrieve translated string (it should be improved with caching values from resource):

    internal static string GetString(string str, string lang)
    {

        if (string.IsNullOrEmpty(str)) throw new ArgumentNullException("empty language query string");
        if (string.IsNullOrEmpty(lang)) throw new ArgumentNullException("no language resource given");

        // culture-specific file, i.e. "LangResources.fr"
        Stream stream = Assembly.GetExecutingAssembly().GetManifestResourceStream("PIAE.LangResources."+lang);

        // resource not found, revert to default resource
        if (null == stream)
        {                                                                   
            stream = Assembly.GetExecutingAssembly().GetManifestResourceStream("PIAE.Properties.LangResources.resources");
        }

        ResourceReader reader = new ResourceReader(stream);
        IDictionaryEnumerator en= reader.GetEnumerator();
        while (en.MoveNext())
        {
            if (en.Key.Equals(str))
            {
                return en.Value.ToString();
            }
        }

        // string not translated, revert to default resource
        return LangResources.ResourceManager.GetString(str);
    }

You didn't find it because it's not the way the .NET framework works. .NET expects satellite DLLs in specifically named location (iow directories named after the language of the resources it contains. eg. de, de-DE, chs,...). If you don't work that way, .NET won't be able to apply its magic (which is to automatically pick the correct resource according to the current UI culture: Thread.CurrentThread.CurrentUICulture).