在自定义控件中公开ItemContainerGenerator的优雅方式

public class CustomControl : Control
{
    public static readonly DependencyProperty ItemContainerGeneratorProperty =
        DependencyProperty.Register(nameof(ItemContainerGenerator), typeof(ItemContainerGenerator), typeof(CustomControl),
            new PropertyMetadata(null));

    public ItemContainerGenerator ItemContainerGenerator
    {
        get { return (ItemContainerGenerator)GetValue(ItemContainerGeneratorProperty); }
        set { SetValue(ItemContainerGeneratorProperty, value); }
    }

    public override void OnApplyTemplate()
    {
        base.OnApplyTemplate();

        // 在模板应用时获取ItemContainerGenerator
        ItemContainerGenerator = GetItemContainerGeneratorFromVisualTree();
    }

    private ItemContainerGenerator GetItemContainerGeneratorFromVisualTree()
    {
        // 在这里获取ItemContainerGenerator的实例
        // 你可以使用VisualTreeHelper等方法来遍历控件的可视化树，找到包含ItemContainerGenerator的元素

        // 示例代码：
        var itemsPresenter = GetVisualChild<ItemsPresenter>(this);
        return itemsPresenter?.ItemContainerGenerator;
    }

    private T GetVisualChild<T>(DependencyObject parent) where T : DependencyObject
    {
        var childCount = VisualTreeHelper.GetChildrenCount(parent);
        for (int i = 0; i < childCount; i++)
        {
            var child = VisualTreeHelper.GetChild(parent, i);
            if (child is T typedChild)
                return typedChild;

            var foundChild = GetVisualChild<T>(child);
            if (foundChild != null)
                return foundChild;
        }

        return null;
    }
}