public String Cau03_AJAX_GetPlaylist(String MaNN)
        {
            StoreContext    storeContext = HttpContext.RequestServices.GetService(typeof(StoreContext)) as StoreContext;
            List <PlayList> playlists    = storeContext.GetPlaylistByMaNN(MaNN);

            return(JsonConvert.SerializeObject(playlists));
        }