public async Task <IActionResult> AddNotificationList(IEnumerable <UserNotificationDTO> userNotifications) { IEnumerable <UserNotificationDTO> AddedUserNotifications; try { AddedUserNotifications = await _notificationService.AddListUserNotificationAsync(userNotifications); } catch (InvalidOperationException) { return(BadRequest()); } var tasks = GetOnlineUserFromList(AddedUserNotifications).Select(un => SendPrivateNotification(un)); await Task.WhenAll(tasks); return(NoContent()); }