public SelectMultipleItemsPopUp(SelectMultipleItemsViewModel viewModel)
        {
            InitializeComponent();

            this.BindingContext = viewModel;
            this.CloseWhenBackgroundIsClicked = false;
        }
        public SelectMultipleItems()
        {
            InitializeComponent();

            this.Content.BindingContext = this.ViewModel = new SelectMultipleItemsViewModel(this);
            this.LabelItems.GestureRecognizers.Add(new TapGestureRecognizer {
                Command = new Command(async() => {
                    await PopupNavigation.PushAsync(new SelectMultipleItemsPopUp(this.ViewModel));
                })
            });
        }