LINQ to XML查询中的基本过滤 [英] Basic filtering in LINQ to XML Queries

问题描述

我是XDocument和LINQ的新手.这是我正在尝试做的事情:

I am new to XDocument and LINQ. Here is what I am trying to do :

XML文件:

<?xml version="1.0" encoding="utf-8"?>
<root>
  <chapters total-chapters="3">
    <Chapter chapter-no="1">
      <chapter-summary>this is chapter 1</chapter-summary>
    </Chapter>
    <Chapter chapter-no="2">
      <chapter-summary>this is chapter 2</chapter-summary>
    </Chapter>
    <Chapter chapter-no="3">
      <chapter-summary>this is chapter 3</chapter-summary>
    </Chapter>
    <Chapter chapter-no="4">
      <chapter-summary>this is chapter 4</chapter-summary>
    </Chapter>
</chapters>
</root>

现在，我需要阅读所有带有特定章节编号的记录.我将LINQ查询编写为:

Now I need to read all the records with a specific chapter-no. I am writing my LINQ query as :

IEnumerable<XElement> elem_list = 
    from e in xdoc.Elements("Chapter") 
    where (string) e.Attribute("chapter-no") == "1" 
    select e;

foreach (XElement e in elem_list)
{
    Console.WriteLine(e);
}

但是elem_list没有填充，并且什么也不显示.

but elem_list is not getting populated and nothing is displayed.

推荐答案

.Elements("Chapter")仅在当前元素的直接子代(xdoc的根)内搜索.

.Elements("Chapter") search only within direct children of current element (root for xdoc).

您可以使用.Descendants("Chapter"):

IEnumerable<XElement> elem_list = from e in xdoc.Descendants("Chapter")
                                  where (string) e.Attribute("chapter-no") == "1"
                                  select e;

或指定完整的项目路径:

Or specify full item path:

IEnumerable<XElement> elem_list = from e in xdoc.Root.Element("chapters").Elements("Chapter")
                                  where (string) e.Attribute("chapter-no") == "1"
                                  select e;

另一种方法-使用XPath选择器:

Another approach - with XPath selector:

xdoc.XPathSelectElements("root/chapters/Chapter[@chapter-no=1]");

using System.Xml.XPath;是使最后一个示例工作所必需的.

using System.Xml.XPath; is necessary to make the last sample work.

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