public async Task AcceptFriendInvitationAsync(Guid invitingUserId, Guid invitedUserId) { if (!await _friendRepository.SetFriendInvitationStatusAsync(invitingUserId, invitedUserId, Models.Enums.FriendInvitationStatus.Accepted)) { throw new DataAccessException($"Accepting friend invitation failed for model: {JsonConvert.SerializeObject(new { invitedUserId, invitingUserId })}"); } var checkInvitersNumberOfFriendsTask = _achievementService.CheckForNumberOfFriendsAsync(invitingUserId); var checkReceiversNumberOfFriendsTask = _achievementService.CheckForNumberOfFriendsAsync(invitedUserId); await Task.WhenAll(checkInvitersNumberOfFriendsTask, checkReceiversNumberOfFriendsTask); }