public ActionResult _AddGroupUsers(string id_group, List <string> selected_userGroup_id) { if (ModelState.IsValid) { //Getting data to post List <GroupUserDTO> groupUserDTOList = new List <GroupUserDTO>(); foreach (var user_id in selected_userGroup_id) { GroupUserDTO groupUserDTO = new GroupUserDTO(); groupUserDTO.id_group = id_group; groupUserDTO.user_id = user_id; groupUserDTOList.Add(groupUserDTO); } //Post List <GroupUserDTO> groupUsersAdded = new List <GroupUserDTO>(); List <GroupUserDTO> groupUserError = new List <GroupUserDTO>(); groupUsersAdded = groupProvider.postUsersGroups(groupUserDTOList).Result; if (groupUsersAdded.Count != 0) { //Compare and get not added users foreach (var user_added in groupUsersAdded) { bool isAdded = false; foreach (var user_id in selected_userGroup_id) { if (user_id == user_added.user_id) { isAdded = true; break; } } if (!isAdded) { groupUserError.Add(user_added); groupUsersAdded.Remove(user_added); } } // creates a json to return result var result = new { usersAdded = groupUsersAdded, usersError = groupUserError, viewHtml = PartialView("/Views/Users/_Group/_GroupUsersList.cshtml", new Model.GroupModel(id_group)).RenderToString() }; return(Json(result)); } } return(new HttpStatusCodeResult(404, "Repeated users")); }