public SPpage()
        {
            InitializeComponent();
            VendorPage vp = new VendorPage();

            vendorframe.NavigationService.Navigate(vp);
            CustomerTab cl = new CustomerTab();

            customerFrame.NavigationService.Navigate(cl);
            StockPage sp = new StockPage();

            frameStock.NavigationService.Navigate(sp);
            ExpenseAccountPage eap = new ExpenseAccountPage();

            ExpenseFrame.NavigationService.Navigate(eap);
            ChartPage cp = new ChartPage();

            chartFrame.NavigationService.Navigate(cp);
        }
        private void btn_Back_Click(object sender, RoutedEventArgs e)
        {
            ExpenseAccountPage eap = new ExpenseAccountPage();

            this.NavigationService.Navigate(eap);
        }