public ActionResult Index(SuperheroViewModel model)
        {
            if (String.IsNullOrWhiteSpace(model.Name))
            {
                ModelState.AddModelError("Name", "Name cannot be empty.");
            }

            if (model.Skills.Count > 3)
            {
                ModelState.AddModelError("Skills", "Skills cannot be more than 3.");
            }

            if (!model.CurrentTeams.Any())
            {
                ModelState.AddModelError("CurrentTeams", "Superhero must be assigned to a team.");
            }

            if (!ModelState.IsValid)
            {
                return View("Index", model);
            }

            // todo

            return View("Notification", (Object)"Superhero has been added successfully.");
        }
        public SuperheroViewModel(SuperheroViewModel other)
        {
            if (other == null) throw new ArgumentNullException(nameof(other));

            Name = other.Name;
            NewSkill = other.NewSkill;
            Skills = other.Skills;
            AvailableTeams = other.AvailableTeams;
            CurrentTeams = other.CurrentTeams;
        }
        public ActionResult Index()
        {
            var model = new SuperheroViewModel()
            {
                AvailableTeams = new List<String>
                {
                    "Justice League",
                    "Batman Incorporation",
                    "Teen Titans",
                    "Suicide Squad"
                }
            };

            return View("Index", model);
        }