public ContactListPage()
        {
            Title = "My Contacts";

            NavigationPage.SetHasNavigationBar(this, true);

            listView = new ListView
            {
                RowHeight = 40,
                ItemTemplate = new DataTemplate(typeof(ContactCell))
            };

            listView.ItemSelected += (sender, e) =>
            {
                var contact = (Contact)e.SelectedItem;
                var contactPage = new ContactPage();
                contactPage.BindingContext = contact;
                Navigation.PushAsync(contactPage);
            };

            var layout = new StackLayout();

            layout.Children.Add(listView);
            layout.VerticalOptions = LayoutOptions.FillAndExpand;
            Content = layout;
            ToolbarItem tbi = null;
            if (Device.OS == TargetPlatform.iOS)
            {
                tbi = new ToolbarItem("+", null, () =>
                {
                    var contact = new Contact();
                    var contactPage = new ContactPage();
                    contactPage.BindingContext = contact;
                    Navigation.PushAsync(contactPage);
                }, 0, 0);
            }
            if (Device.OS == TargetPlatform.Android)
            {
                tbi = new ToolbarItem("+", "plus", () =>
                {
                    var contact = new Contact();
                    var contactPage = new ContactPage();
                    contactPage.BindingContext = contact;
                    Navigation.PushAsync(contactPage);
                }, 0, 0);
            }

            ToolbarItems.Add(tbi);
        }