public MainWindow() { InitializeComponent(); BIZ = new ClassBIZ(); UCC = new UserControlCustomer(BIZ); UCDP = new UserControlDailyPrice(BIZ); UCD = new UserControlDiesel(BIZ); UCS = new UserControlSupplier(BIZ); // We add the usercontrols as children of each of the respective grid from the tabs CustomerGrid.Children.Add(UCC); DailyPriceGrid.Children.Add(UCDP); SalesGrid.Children.Add(UCD); SupplierGrid.Children.Add(UCS); BIZ.CallWebApi(); }