private void InitializeStoreData()
        {
            _itemsList = _manager.GetItemsInStore();
            Thread.Sleep(5);
            var page = new SelectItemsPage(_manager);

            this.NavigationService.Navigate(page);
        }
        /*---------------------------------*/

        private void button_Click(object sender, RoutedEventArgs e)
        {
            if (suppliersList.Contains(supplier_textBox.Text))
            {
                _manager.SetSelection(supplier_textBox.Text, branch_textBox.Text);
                var page2 = new SelectItemsPage(_manager);
                this.NavigationService.Navigate(page2);
            }
        }