public IEnumerable <ProfileDto> GetFollowers(string userName) { if (userName.IsNullOrEmpty()) { throw new ArgumentNullException(nameof(userName)); } var followers = _profileProvider.GetFollowersByUserName(userName); return(followers.Select(x => { var result = _mapper.Map <ProfileDto>(x); result.Followers = x.Followers.Select(p => _mapper.Map <ProfileDto>(p)).ToList(); return result; })); }