public async Task AddFriendToCharacterAsync(Character character, Character friend) { if (_characterRepository.HasFriendAlready(character, friend)) { throw new InvalidOperationException($"{friend?.Name} is already friend of {character.Name}"); } if (character.Id == friend.Id) { throw new InvalidOperationException($"Cannot add friend of myself"); } _characterRepository.AddFriendToCharacter(character, friend); await _characterRepository.SaveChangesAsync(); }