public async Task TrackDeliveredAsync(IEnumerable <TrackingToken> tokens) { await userNotificationsStore.TrackDeliveredAsync(tokens); foreach (var token in tokens.Where(x => x.IsValid && !string.IsNullOrWhiteSpace(x.Channel))) { var channel = channels.FirstOrDefault(x => x.Name == token.Channel); if (channel != null) { await channel.HandleDeliveredAsync(token); } } }