public static string[] GetGroups(int id)
{
    XDocument doc = XDocument.Load(
        $"https://api.vk.com/method/groups.get.xml?user_id={id}&extended=1&count=100" +
        "&access_token=" + token);
    var groups = doc.Root.Elements("group").Elements("name").Select(e => e.Value).ToArray();
    return groups;
}