private async void zakazi_Clicked(object sender, EventArgs e)
        {
            try
            {
                var      trm            = Termini.Items[Termini.SelectedIndex];
                var      datum          = Datum;
                var      selectedTermin = Termini.Items[Termini.SelectedIndex];
                var      hours          = int.Parse(selectedTermin.Split(':')[0]);
                var      minutes        = int.Parse(selectedTermin.Split(':')[1]);
                TimeSpan ts             = new TimeSpan(hours, minutes, 0);
                var      stringDate     = datum.Date.ToString();
                var      newDatum       = DateTime.Parse(stringDate) + ts;

                var pregled = new KorisnikPregled.PreglediVM
                {
                    Datum      = newDatum,
                    KorisnikID = CurrentUser.User.Id,
                    OdjelID    = _odjelID
                };

                await Navigation.PushAsync(new PlacanjePage(pregled));
            }
            catch
            {
                await Application.Current.MainPage.DisplayAlert
                    ("Greška", "Izaberite termin pregleda", "OK");
            }
        }
        public PlacanjePage(KorisnikPregled.PreglediVM pregled)
        {
            InitializeComponent();
            _pregled = pregled;
            var nav = new NavigationPage(new AboutPage());

            navigation     = nav.Navigation;
            BindingContext = model = new PaymentVM(_pregled, navigation);
        }