获取XPath到XElement？

using System;
using System.Xml.Linq;
using System.Xml.XPath;

class Program
{
    static void Main(string[] args)
    {
        XElement element = new XElement("book",
            new XElement("title", "The Grapes of Wrath"),
            new XElement("author", "John Steinbeck")
        );

        string xpath = GetXPath(element);
        Console.WriteLine(xpath);
    }

    static string GetXPath(XElement element)
    {
        string xpath = "";
        XElement currentElement = element;

        while (currentElement != null)
        {
            int index = GetElementIndex(currentElement);
            string elementName = currentElement.Name.LocalName;

            if (index > 0)
            {
                xpath = $"/{elementName}[{index + 1}]" + xpath;
            }
            else
            {
                xpath = $"/{elementName}" + xpath;
            }

            currentElement = currentElement.Parent;
        }

        return xpath;
    }

    static int GetElementIndex(XElement element)
    {
        int index = 0;

        foreach (XElement sibling in element.Parent.Elements(element.Name))
        {
            if (sibling == element)
            {
                return index;
            }

            index++;
        }

        return -1;
    }
}