pkNX/pkNX.WinForms/Themes/TreeViewItemExtensions.cs

using System.Windows;
using System.Windows.Controls;
using System.Windows.Media;

namespace DarkBlendTheme;

public static class TreeViewItemExtensions
{
    public static int GetDepth(this TreeViewItem item)
    {
        while (GetParent(item) is { } parent)
        {
            return GetDepth(parent) + 1;
        }
        return 0;
    }

    private static TreeViewItem? GetParent(DependencyObject item)
    {
        var parent = VisualTreeHelper.GetParent(item);

        while (parent is not (TreeViewItem or TreeView))
        {
            if (parent == null)
                return null;
            parent = VisualTreeHelper.GetParent(parent);
        }
        return parent as TreeViewItem;
    }
}