private void MenuAddSaleBill_Click(object sender, RoutedEventArgs e)
        {
            var numberItem = TabControl_AddSaleBills.Items.Count;

            if (numberItem >= maxAddSaleBillTab)
            {
                MessageBox.Show("Số tab tạo hóa đơn tối đa là !" + maxAddSaleBillTab, "Add more", MessageBoxButton.OK, MessageBoxImage.Warning);
                return;
            }
            ////reset the list of tab titles
            for (int i = 0; i < numberItem; i++)
            {
                CustomTabItem currentTab = (CustomTabItem)TabControl_AddSaleBills.Items[i];
                currentTab.Title = GenerateTabTitle(i + 1);
            }
            //Add new tab
            AddSaleBillUserControl addSaleBillUserControl = new AddSaleBillUserControl();
            CustomTabItem          customTabItem          = new CustomTabItem()
            {
                Title = GenerateTabTitle(numberItem + 1), Content = addSaleBillUserControl
            };

            TabControl_AddSaleBills.Items.Add(customTabItem);
            TabControl_AddSaleBills.SelectedItem = customTabItem;
        }
        private void LoadMainTabControl()
        {
            AddSaleBillUserControl addSaleBillUserControl = new AddSaleBillUserControl();
            CustomTabItem          customTabItem          = new CustomTabItem()
            {
                Title = GenerateTabTitle(1), Content = addSaleBillUserControl
            };

            TabControl_AddSaleBills.Items.Clear();
            TabControl_AddSaleBills.Items.Add(customTabItem);
            TabControl_AddSaleBills.SelectedItem = customTabItem;
        }