public partial class TestPopup : Popup
    {
        public User User { get; set; } = new User();
        public List<Position> Positions { get; set; }
        [Inject]
        public PositionHelper PositionHelper { get; set; }

        protected override void OnInitialized()
        {
            Positions = (List<Position>)PositionHelper.GetPositions();
        }

        public override void OnOk()
        {
            //InvokeAsync(() => PopupService.Close(true));
            Console.WriteLine(User);
        }

        void HandleOnChange(Position p)
        {
            User.Position = p;
        }

    }

    public class User
    {
        [Required(ErrorMessage = "Please Enter a First Name")]
        public string FirstName { get; set; }
        [Required(ErrorMessage = "Please Enter a Last Name")]
        public string LastName { get; set; }
        [Required(ErrorMessage = "Please Set a Position")]
        public Position Position { get; set; }
    }