public IActionResult Groups(int?id) { var groups = _groupHandler.GetAll(); ViewBag.Groups = groups; if (id.HasValue)/* in brackets && groups.Any(x=>x.Id == id)*/ { var activeGroup = groups.FirstOrDefault(g => g.Id == id); var users = _usersInGroupHandler.GetUsersByGroup(id.Value); var numberUsers = _groupHandler.GetNumberUsersInGroup(id.Value); var user = _userManager.GetUserId(User); var userName = _userManager.GetUserName(User); List <AppUser> usersInGroup = new List <AppUser>(); foreach (var u in users) { var userInGroupId = _usersInGroupHandler.GetId(u); var user1 = _userManager.Users.FirstOrDefault(k => k.Id == userInGroupId); usersInGroup.Add(user1); } var userInGroup = _usersInGroupHandler.GetUserInGroup(activeGroup.Id, user); ViewBag.Group = activeGroup.GroupName; ViewBag.GroupId = activeGroup.Id; ViewBag.userName = _userManager.GetUserName(User); //ViewBag.Users = users; ViewBag.numberUsers = numberUsers; ViewBag.usersInGroup = usersInGroup; ViewBag.userInGroup = userInGroup; } else { ModelState.AddModelError("error", "Group not found!"); } return(View(_userManager.Users.ToList())); }