public void ChangeCulture(string langue)
{
    CultureInfo ret;
    switch (langue)
    {
        case "N":
            ret = new CultureInfo("nl-NL");
            break;
        case "E":
            ret = new CultureInfo("en-US");
            break;
        case "D":
            ret = new CultureInfo("de-DE");
            break;
        default:
            ret = new CultureInfo("fr-FR");
            break;
    }
    if (ret.NumberFormat.NumberDecimalSeparator != ".")
        ret.NumberFormat.NumberDecimalSeparator = ".";
    if (ret.NumberFormat.NumberGroupSeparator != " ")
        ret.NumberFormat.NumberGroupSeparator = " ";

    System.Threading.Thread.CurrentThread.CurrentUICulture = ret;
    System.Threading.Thread.CurrentThread.CurrentCulture = ret;
}