使用XPath查询从匹配的XML节点获取属性值 [英] Get attribute values from matching XML nodes using XPath query

问题描述

这似乎不应该很困难，但我目前陷入困境.我正在尝试从与给定XPath查询字符串匹配的节点中获取特定属性的属性值.这是我到目前为止的内容:

This doesn't seem like it should be difficult, but I'm stuck currently. I'm trying to get the attribute values for a particular attribute from nodes that match a given XPath query string. Here's what I have so far:

    public static IEnumerable<string> GetAttributes(this XmlDocument xml,
        string xpathQuery, string attributeName)
    {
        var doc = new XPathDocument(new XmlNodeReader(xml));
        XPathNavigator nav = doc.CreateNavigator();
        XPathExpression expr = nav.Compile(xpathQuery);
        XPathNodeIterator iterator = nav.Select(expr);
        while (iterator.MoveNext())
        {
            XPathNavigator curNav = iterator.Current;
            if (curNav.HasAttributes)
            {
                XmlNode curNode = ((IHasXmlNode)curNav).GetNode();
                if (null != curNode)
                {
                    XmlAttribute attrib = curNode.Attributes[attributeName];
                    if (null != attrib)
                    {
                        yield return attrib.Value;
                    }
                }
            }
        }
    }

当前会引发异常:

System.InvalidCastException:无法将类型为"MS.Internal.Xml.Cache.XPathDocumentNavigator"的对象转换为类型为"System.Xml.IHasXmlNode"的对象.

System.InvalidCastException: Unable to cast object of type 'MS.Internal.Xml.Cache.XPathDocumentNavigator' to type 'System.Xml.IHasXmlNode'.

我要解决这个问题吗?有没有更简单的方法来从匹配的节点获取属性值?

Am I going about this wrong? Is there a simpler way to get attribute values from matching nodes?

推荐答案

对于以下xml:

<root>
  <elem att='the value' />
</root>

您可以使用此C#代码获取值"文本

You can get the "the value" text with this C# code

    XmlDocument xdoc = new XmlDocument();
    xdoc.LoadXml(text);
    Console.WriteLine(xdoc.SelectSingleNode("/root/elem/@att").Value);

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