private void Window_Loaded(object sender, RoutedEventArgs e) { TabItem tiNew = new TabItem() { Header = "Outer Tab 1", Content = new DummyClass() { DummyMember = 1 } }; OuterTabs.Items.Add(tiNew); TabItem tiNew2 = new TabItem() { Header = "Outer Tab 2", Content = new DummyClass() { DummyMember = 2 } }; OuterTabs.Items.Add(tiNew2); }