public static ItemsPanelTemplate ItemsPanelTemplate <TRootUI>(Action <Xaml.DependencyObject> build) where TRootUI : Xaml.UIElement, new()
        {
#if WINUI
            // Note that we cannot pass markup objects to the build action here, because we get the ui type instance.
            var ui = (Xaml.Controls.ItemsPanelTemplate)CreateTemplate(nameof(Xaml.Controls.ItemsPanelTemplate), typeof(TRootUI), true, ConfigureRoot.CreateIdFor(build));
#else
            var ui = new Xaml.Controls.ItemsPanelTemplate(() =>
            {
                var root = new TRootUI();
                build(root);
                return(root);
            });
#endif
            return(CSharpMarkup.WinUI.ItemsPanelTemplate.StartChain(ui));
        }
        public static ItemsPanelTemplate ItemsPanelTemplate <TRootUI>(Func <UIElement> build) where TRootUI : Xaml.Controls.Panel, new()
        {
#if WINUI
            var ui = (Xaml.Controls.ItemsPanelTemplate)CreateTemplate(nameof(Xaml.Controls.ItemsPanelTemplate), typeof(TRootUI), false, BuildChild.CreateIdFor(build));
#else
            var ui = new Xaml.Controls.ItemsPanelTemplate(() =>
            {
                var root  = new TRootUI();
                var child = build();
                root.Children.Add(child.UI);
                return(root);
            });
#endif
            return(CSharpMarkup.WinUI.ItemsPanelTemplate.StartChain(ui));
        }