async void LvWebsites_ItemSelected(object sender, SelectedItemChangedEventArgs e)
        {
            if (e.SelectedItem == null)
            {
                return;
            }

            NightScout nsItem = (NightScout)e.SelectedItem;

            MessagingCenter.Send <MasterPage, NightScout>(this, "NightScout", nsItem);
            await Navigation.PushAsync(new DetailPage());



            ((ListView)sender).SelectedItem = null;
        }
        List <NightScout> nsList;       // = new List<NightScout>();

        public MasterPage()
        {
            InitializeComponent();
            nsWebsite = new NightScout();

            BindingContext = nsWebsite;

            NightScout n = new NightScout();

            n.T1DName = "Lydia";
            n.NSURL   = "evaroo.azurewebsites.net";

            nsList = new List <NightScout>();
            nsList.Add(n);
            lvWebsites.ItemsSource = nsList;

            lvWebsites.ItemSelected += LvWebsites_ItemSelected;

            //MessagingCenter.Subscribe<MasterPage>(this,"Add", (obj) => lvWebsites.ItemsSource = nsList);
            btnAdd.Clicked += BtnAdd_Clicked;
        }
        public DetailPage()
        {
            InitializeComponent();

            if (nsWeb == null)
            {
                nsWeb       = new NightScout();
                nsWeb.NSURL = "evaroo.azurewebsites.net";
            }
            MessagingCenter.Subscribe <MasterPage, NightScout>(this, "NightScout", (page, nsItem) =>
            {
                nsWeb = nsItem;
            });



            this.BindingContext = _viewModel = new EventsViewModel();
            BackgroundColor     = Xamarin.Forms.Device.OnPlatform(Xamarin.Forms.Color.White, Xamarin.Forms.Color.White, Xamarin.Forms.Color.Transparent);

            //nsWeb = nsWebsite;
        }