/// <summary>
        /// Возвращает следующую партию оповещений.
        /// </summary>
        /// <param name="count">Количество элементов.</param>
        private async Task <List <IVKNotification> > GetNextNotifications(uint count = 20)
        {
            var parameters = new Dictionary <string, string>();

            parameters["count"] = count.ToString();
            if (!String.IsNullOrEmpty(nextFrom))
            {
                parameters["start_from"] = nextFrom;
            }

            var request  = new UniversalVKRequest <VKNotificationsGetResponse>(VKMethodsConstants.NotificationsGet, parameters);
            var response = await request.ExecuteAsync();

            if (response.Error.ErrorType == VKErrors.None)
            {
                nextFrom = response.Response.NextFrom;
                return(response.Response.Items);
            }
            else
            {
                return(null);
            }
        }