How to update just a single column of table in MVC5 ?

public string CloseDay(string date)
        {
            string Message = string.Empty;
            try
            {
                Session session = new Session();
                session.Status = "C";
                //db.Update<Session>(session.Status, a => a.SessionDate == Convert.ToDateTime(date));
                db.Update<Session>(session, a => a.SessionDate == Convert.ToDateTime(date));
                Message = "Day Closed Successfully";
            }
            catch (Exception Ex){ Message = Ex.Message; }
            return Message;
        }