how to post to all Facebook groups using SDK C#

public static bool Postfr(string AccessToken, string Friendwall, string groupId, string Link = "")
        {

            try
            {
                FacebookClient fb = new FacebookClient(AccessToken);
                var obj = fb.Get(
"https://graph.facebook.com/ur_postid?access_token=ur_accesstoken");
                Dictionary<string, object> POST = new Dictionary<string, object>();
                POST["message"] = message;
                if (Link != "")
                {
                    POST["link"] = Link;
                }

                fb.Post("{group-id}/feed", POST);
                return true;

            }
            catch (Exception ex)
            {
                System.Windows.Forms.MessageBox.Show(ex.Message);
                return true;

            }

        }