C# 無法查詢 XML 但可以遍歷節點？

Question

與我的其他問題有關。

我正在嘗試從 XML 文件中讀取一個節點，如下所示：

<?xml version="1.0" encoding="UTF-8" ?>
<AuthorIT>
    <Objects>
        <Media>don't care</Media>
        <Style>don't care</Style>
        <Book>don't care</Book>
        <Topic>don't care</Topic>
        <Topic>
            <Object>
                <Description>Performance Evidence</Description>
            </Object>
            <Text>This is what I want to select</Text>
        </Topic>
    </Objects>
</AuthorIT>

但我無法查詢。 我試過 XmlDocument、XPath 和 Linq 到 XML。

我已經在http://XPather.com上驗證了我的 XPath 是正確的。

            /* this doesn't work but the XPath has been verified */
            XPathNavigator nav;
            XPathDocument docNav;
            string xPath;

            docNav = new XPathDocument(localFile);
            nav = docNav.CreateNavigator();
            xPath = "//Topic[Object/Description = 'Performance Evidence']/Text";
            string value = nav.SelectSingleNode(xPath).Value;

我可以使用 XmlDocument 遍歷 XML 節點，但我不希望使用一系列嵌套的 foreach 循環來代替單個查詢。

 XmlDocument doc = new XmlDocument();
 doc.Load(localFile);
 XmlNodeList xmlNodes = doc.SelectNodes("/");

 /* direct query doesn't work, but traversing the nodes does? */
 foreach (XmlNode node in xmlNodes)
 {
     if (node.Name == "#document")
     {
         foreach (XmlNode subNode in node.ChildNodes)
         {
             if (subNode.Name == "AuthorIT")
             {
                 foreach (XmlNode subSubNode in subNode.ChildNodes)
                 {
                     if (subSubNode.Name == "Objects")
                     {
                         foreach (XmlNode subSubSubNode in subSubNode.ChildNodes)
                         {
                             if (subSubSubNode.Name == "Topic")
                             {
// I didn't finish writing this, because it's a ridiculous way to do it... but it works
                             }
                         }
                     }
                 }
             }
         }
     }
 }

有什么我做錯了嗎？

XML 文檔的某些屬性會導致這種情況嗎？ （如果是這樣，我該如何解決？）

Answer 1

如果您想要的只是存儲在<Text>屬性中的值，則無需遍歷所有內容，請嘗試以下操作：

var doc = XDocument.Parse(File.ReadAllText(filePath));
var value = doc.XPathSelectElement("/AuthorIT/Objects/Topic/Text").Value;

Answer 2

我在示例 XML 中遺漏的是解決方案的關鍵......命名空間！

我在另一個問題上找到了答案： Using Xpath With Default Namespace in C#