Random r = new Random();
string[] acceptLanguageSet = {
"ru-RU,ru;q=0.8",
"ru-RU,ru;q=0.9",
"ru-RU,ru;q=0.8",
};
// Устанавливаем Accept-Language
string acceptLanguage = acceptLanguageSet[r.Next(0, acceptLanguageSet.Length)].ToString();
project.Profile.AcceptLanguage = acceptLanguage;
// Устанавливаем настройки языка
project.Profile.UserAgentBrowserLanguage = acceptLanguage.Substring(0, acceptLanguage.IndexOf(','));
project.Profile.UserAgentLanguage = acceptLanguage.Substring(0, acceptLanguage.IndexOf(','));