public async Task <IEnumerable <Participant> > CreateRangeAsync(ParticipantRange range, ApplicationUser user, Action <string, string> AddErrorMessage) { if (range.Users == null || range.Users.Count == 0) { return(null); } if (user == null) { AddErrorMessage?.Invoke("General", "Only Logged-in user can perform this operation"); return(null); } Chatroom chatroom = await _chatroomService.GetAsync(range.ChatroomID); if (user.Id != chatroom.OwnerID) { AddErrorMessage?.Invoke("General", "Only Owner of a Chatroom can add participants!"); return(null); } List <ParticipantEntity> participants = new List <ParticipantEntity>(); foreach (UserShort u in range.Users) { ParticipantEntity temp = new ParticipantEntity { ChatroomID = range.ChatroomID, UserID = u.UserID, User = new ApplicationUser { Id = u.UserID, UserName = u.UserName }, }; _context.Entry(temp.User).State = EntityState.Unchanged; participants.Add(temp); } IEnumerable <ParticipantEntity> created = await _repository.CreateRangeAsync(participants); if (created != null && created.Any()) { await _context.SaveChangesAsync(); } IEnumerable <Participant> result = _mappingService.EntitiesToDtos(created); foreach (Participant p in result) { p.Deletable = (p.UserID != user.Id); } return(result); }