如何将 XPath 与 XDocument 一起使用？

如果您有 XDocument，则使用 LINQ-to-XML 会更容易：

var document = XDocument.Load(fileName);
var name = document.Descendants(XName.Get("Name", @"http://demo.com/2011/demo-schema")).First().Value;

如果您确定 XPath 是您需要的唯一解决方案：

using System.Xml.XPath;

var document = XDocument.Load(fileName);
var namespaceManager = new XmlNamespaceManager(new NameTable());
namespaceManager.AddNamespace("empty", "http://demo.com/2011/demo-schema");
var name = document.XPathSelectElement("/empty:Report/empty:ReportInfo/empty:Name", namespaceManager).Value;

MS 实现的 XPath 1.0 没有默认命名空间的概念。所以试试这个：

XDocument xdoc = XDocument.Load(@"C:\SampleXML.xml");
XmlNamespaceManager xnm = new XmlNamespaceManager(new NameTable()); 
xnm.AddNamespace("x", "http://demo.com/2011/demo-schema");
Console.WriteLine(xdoc.XPathSelectElement("/x:Report/x:ReportInfo/x:Name", xnm) == null);

您可以使用 Microsoft 中的示例 - 对于没有命名空间的您：

using System.Xml.Linq;
using System.Xml.XPath;
var e = xdoc.XPathSelectElement("./Report/ReportInfo/Name");     

应该这样做

要在没有默认命名空间后缀的情况下工作，我会自动扩展路径。

用法：SelectElement(xdoc.Root, "/Report/ReportInfo/Name");

private static XElement SelectElement(XElement startElement, string xpathExpression, XmlNamespaceManager namespaceManager = null) {
    // XPath 1.0 does not have support for default namespace, so we have to expand our path.
    if (namespaceManager == null) {
        var reader = startElement.CreateReader();
        namespaceManager = new XmlNamespaceManager(reader.NameTable);
    }
    var defaultNamespace = startElement.GetDefaultNamespace();
    var defaultPrefix = namespaceManager.LookupPrefix(defaultNamespace.NamespaceName);
    if (string.IsNullOrEmpty(defaultPrefix)) {
        defaultPrefix = "ᆞ";
        namespaceManager.AddNamespace(defaultPrefix, defaultNamespace.NamespaceName);
    }
    xpathExpression = AddPrefix(xpathExpression, defaultPrefix);
    var selected = startElement.XPathSelectElement(xpathExpression, namespaceManager);
    return selected;
}

private static string AddPrefix(string xpathExpression, string prefix) {
    // Implementation notes:
    // * not perfect, but it works for our use case.
    // * supports: "Name~~" "~~/Name~~" "~~@Name~~" "~~[Name~~" "~~[@Name~~"
    // * does not work in complex expressions like //*[local-name()="HelloWorldResult" and namespace-uri()='http://tempuri.org/']/text()
    // * does not exclude strings like 'string' or function like func()
    var s = Regex.Replace(xpathExpression, @"(?<a>/|\[@|@|\[|^)(?<name>\w(\w|[-])*)", "${a}${prefix}:${name}".Replace("${prefix}", prefix));
    return s;
}

如果有人有更好的解决方案来查找元素和属性名称，请随时更改此帖子。