哪个是性能最佳的:带XPath的XPathNavigator vs带有查询的Linq到Xml？

Question

我有一个应用程序,我使用XPathNavigator迭代节点.它工作正常.

但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. 有了XPath,LINQ到Xml的性能如何？

我正在使用C#.net,VS 2010,我的.xml是中等大小.

Answer 1

只是为了添加已经在此处陈述的内容,整体性能似乎取决于您对相关文档的实际操作.这是我基于简单的实验运行得出的结果,比较了XElement与XPathNavigator之间的解析性能.

如果要选择节点,则遍历这些节点并读取某些属性值:

• XElement.Element比XElement.CreateNavigator.Select快大约1.5倍.
• XElement.CreateNavigator.Select比XPathNavigator.Select快大约0.5倍.
• XPathNavigator.Select比XElement.XPathSelectElement快大约0.5倍.

另一方面,如果您还在阅读每个节点的子节点的值,它会变得有趣:

• 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);
    }

从这里下载books.xml

总的来说,如果您的文档有些扁平,看起来XElement解析API(不包括XPath扩展)可以提供最佳性能,同时也更易于使用.如果你有深层嵌套结构,你必须做类似的事情

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

然后XElement.XPathSelectElement可以提供性能和代码可维护性之间的最佳折衷.

Answer 2

嗯，XPathNavigator通常会比Linq to XML查询更快。但总有“但是”。

Linq to XML肯定会让你的代码更具可读性和可维护性。阅读 linq 查询然后分析 XPath 更容易（至少对我来说）。另外 - 在编写查询时您将获得智能感知，这将有助于使您的代码正确。Linq to XML如果您需要的话，还可以让您轻松修改数据。XPathNavigator为您提供只读访问权限。

另一方面，如果您确实需要顶级性能，XPathNavigator这可能是正确的选择。这仅取决于您当前的情况以及您想要实现的目标。如果性能不是问题（XML 文件相当小，您不会对此文件发出很多请求等等），您可以轻松使用Linq to XML. 否则坚持接近XPathNavigator。