private void toVisitBtn_Clicked(object sender, EventArgs e)
        {
            EventToVisitIndexModel eventToVisit = new EventToVisitIndexModel
            {
                EventID      = this.eventID,
                PosjetilacID = Global.PrijavljeniKorisnik.KorisnikID
            };

            //DisplayAlert("nesto", JsonConvert.SerializeObject(eventToVisit), "ok");

            try {
                System.Net.Http.HttpResponseMessage response = eventToVisitService.PostResponse(eventToVisit);

                if (response.IsSuccessStatusCode)
                {
                    DisplayAlert("success", "Oznacili ste dogadjaj sa ToVisit!", "OK");
                    toVisitBtn.IsVisible = false;

                    this.Navigation.PushAsync(new MainPage());
                }
                else
                {
                    DisplayAlert("error", "error", "error");
                }
            }
            catch (Exception ex)
            {
                DisplayAlert("ex", "ex", "ex");
            }
        }
        private void eventList_ItemTapped(object sender, ItemTappedEventArgs e)
        {
            EventToVisitIndexModel eventToVisit = e.Item as EventToVisitIndexModel;

            this.Navigation.PushAsync(new Events.EventToVisitDetails(eventToVisit.EventID));
        }