c# - 哪个是性能最好的 : XPathNavigator with XPath vs Linq to Xml with query?

Question

我有一个应用程序，我在其中使用 XPathNavigator 来迭代节点。它工作正常。

但是我想知道如果我使用 LINQ to Xml....

1. 我会得到什么好处(性能、可维护性)？

2. 使用 XPath、LINQ to Xml 对性能有何影响？

我使用的是 C#.net、VS 2010，我的 .xml 是中等大小。

Answer 1

只是补充一下这里已经说明的内容，整体性能似乎取决于您实际对相关文档执行的操作。这是我根据比较 XElement 和 XPathNavigator 之间的解析性能的简单实验运行得出的结论。

如果是选择节点，遍历这些节点，读取一些属性值:

• XElement.Element 比 XElement.CreateNavigator.Select 快近似系数 1.5。
• XElement.CreateNavigator.Select 更快比 XPathNavigator.Select 大约高出 0.5。
• XPathNavigator.Select 比 XElement.XPathSelectElement 快大约为 0.5。

另一方面，如果您还读取每个节点的子节点的值，它会变得有点有趣:

• XElement.Element 比 XElement.XPathSelectElements 快大约 0.5 倍。
• XElement.XPathSelectElement 比 XPathNavigator.Select 快大约 3 倍。
• XPathNavigator.Select 比 XElement.CreateNavigator.Select 快大约 0.5 倍。

这些结论基于以下代码:

 [Test]
    public void CompareXPathNavigatorToXPathSelectElement()
    {     
        var max = 100000;

        Stopwatch watch = new Stopwatch();
        watch.Start();

        bool parseChildNodeValues = true;

        ParseUsingXPathNavigatorSelect(max, watch, parseChildNodeValues);
        ParseUsingXElementElements(watch, max, parseChildNodeValues);
        ParseUsingXElementXPathSelect(watch, max, parseChildNodeValues);
        ParseUsingXPathNavigatorFromXElement(watch, max, parseChildNodeValues);
    }

    private static void ParseUsingXPathNavigatorSelect(int max, Stopwatch watch, bool parseChildNodeValues)
    {
        var document = new XPathDocument(@"data\books.xml");
        var navigator = document.CreateNavigator();

        for (var i = 0; i < max; i++)
        {
            var books = navigator.Select("/catalog/book");
            while (books.MoveNext())
            {
                var location = books.Current;
                var book = new Book();
                book.Id = location.GetAttribute("id", "");

                if (!parseChildNodeValues) continue;

                book.Title = location.SelectSingleNode("title").Value;
                book.Genre = location.SelectSingleNode("genre").Value;
                book.Price = location.SelectSingleNode("price").Value;
                book.PublishDate = location.SelectSingleNode("publish_date").Value;
                book.Author = location.SelectSingleNode("author").Value;
            }
        }

        watch.Stop();
        Console.WriteLine("Time using XPathNavigator.Select = " + watch.ElapsedMilliseconds);
    }

    private static void ParseUsingXElementElements(Stopwatch watch, int max, bool parseChildNodeValues)
    {
        watch.Restart();
        var element = XElement.Load(@"data\books.xml");

        for (var i = 0; i < max; i++)
        {
            var books = element.Elements("book");
            foreach (var xElement in books)
            {
                var book = new Book();
                book.Id = xElement.Attribute("id").Value;

                if (!parseChildNodeValues) continue;

                book.Title = xElement.Element("title").Value;
                book.Genre = xElement.Element("genre").Value;
                book.Price = xElement.Element("price").Value;
                book.PublishDate = xElement.Element("publish_date").Value;
                book.Author = xElement.Element("author").Value;
            }
        }

        watch.Stop();
        Console.WriteLine("Time using XElement.Elements = " + watch.ElapsedMilliseconds);
    }

    private static void ParseUsingXElementXPathSelect(Stopwatch watch, int max, bool parseChildNodeValues)
    {
        XElement element;
        watch.Restart();
        element = XElement.Load(@"data\books.xml");

        for (var i = 0; i < max; i++)
        {
            var books = element.XPathSelectElements("book");
            foreach (var xElement in books)
            {
                var book = new Book();
                book.Id = xElement.Attribute("id").Value;

                if (!parseChildNodeValues) continue;

                book.Title = xElement.Element("title").Value;
                book.Genre = xElement.Element("genre").Value;
                book.Price = xElement.Element("price").Value;
                book.PublishDate = xElement.Element("publish_date").Value;
                book.Author = xElement.Element("author").Value;
            }
        }

        watch.Stop();
        Console.WriteLine("Time using XElement.XpathSelectElement = " + watch.ElapsedMilliseconds);
    }

    private static void ParseUsingXPathNavigatorFromXElement(Stopwatch watch, int max, bool parseChildNodeValues)
    {
        XElement element;
        watch.Restart();
        element = XElement.Load(@"data\books.xml");

        for (var i = 0; i < max; i++)
        {
            // now we can use an XPath expression
            var books = element.CreateNavigator().Select("book");

            while (books.MoveNext())
            {
                var location = books.Current;
                var book = new Book();
                book.Id = location.GetAttribute("id", "");

                if (!parseChildNodeValues) continue;

                book.Title = location.SelectSingleNode("title").Value;
                book.Genre = location.SelectSingleNode("genre").Value;
                book.Price = location.SelectSingleNode("price").Value;
                book.PublishDate = location.SelectSingleNode("publish_date").Value;
                book.Author = location.SelectSingleNode("author").Value;
            }
        }

        watch.Stop();
        Console.WriteLine("Time using XElement.Createnavigator.Select = " + watch.ElapsedMilliseconds);
    }

使用从 here 下载的 books.xml

总的来说，如果您的文档有点扁平，看起来 XElement 解析 API(不包括 XPath 扩展)可为您提供最佳性能，同时也更易于使用。如果你有很深的嵌套结构，你必须做类似的事情

XElement.Element("book").Element("author").Element("firstname").SomethingElse()

那么 XElement.XPathSelectElement 可能会在性能和代码可维护性之间提供最佳折衷。