問題描述

XML文件的結構大致如下:

The structure of the XML file is more or less as follows:

<?xml version="1.0" encoding="UTF-8"?>
<a xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="url1" xsi:schemaLocation="url2 url3">
   <b>
     <c></c>
     <c></c>
     <c></c>
   </b>
</a>

我的目標是選擇所有c"元素，但以下 xpath 表達式不起作用://a/b/c".

My goal is to select all the "c" elements, but the following xpath expression won't work: "http://a/b/c".

即:

XmlDocument doc= new XmlDocument();
doc.Load(filepath);
XmlNodeList l = doc.SelectNodes("http://a/b/c"); // 0 nodes

我測試過的唯一有效的 xpath 表達式是/*(1 個節點)和//*(所有節點).

The only xpath expressions I tested that worked are /* (1 node) and //* (all nodes).

這個問題與 XML 命名空間有關嗎?如果是這樣，設置 XMLDocument 對象的正確方法是什么?

Is this problem related to the XML namespace? If so, what's the proper way to set up the XMLDocument object?

        XmlDocument doc= new XmlDocument();
        doc.Load(filepath);
        XmlNamespaceManager m = new XmlNamespaceManager(doc.NameTable);
        m.AddNamespace(/* what goes here? */);
        XmlNodeList l = doc.SelectNodes("http://a/b/c", m);

推薦答案

你需要為文檔使用的默認命名空間分配一個命名空間前綴，然后在你的 XPath 中使用它:

You need to assign a namespace prefix for the default namespace that the document is using, and then use that in your XPath:

XmlDocument doc= new XmlDocument();
doc.Load(filepath);

XmlNamespaceManager m = new XmlNamespaceManager(doc.NameTable);
m.AddNamespace("myns", "url1");

XmlNodeList l = doc.SelectNodes("/myns:a/myns:b/myns:c", m);

您可以將前綴myns"替換為基本上任何內容(不帶空格的字母數字)，只要它在第 4 行和 XPath 之間保持一致，并且正確分配給第 4 行中的url1"命名空間.

You can replace the prefix "myns" with essentially anything (alphanumeric without spaces), as long as it's consistent between line 4 and the XPath, and that it's correctly assigned to the "url1" namespace in line 4.

這篇關于如何選擇使用默認命名空間的節點?的文章就介紹到這了，希望我們推薦的答案對大家有所幫助，也希望大家多多支持html5模板網！