使用LINQ-to-XML通过xpath查找或创建元素

Question

Does anyone have a neat way of finding or creating an XObject using an xpath expression. 有没有人使用xpath表达式找到或创建XObject的简洁方法。

The problem I am having is that I need to set a value on an element (which I have the xpath for), which may or not be in existence. 我遇到的问题是我需要在一个元素（我有xpath）上设置一个值，这个值可能存在也可能不存在。 If it's not in existence I would like it to be created. 如果它不存在，我希望它被创建。

Any hints or links would be very much appreciated. 非常感谢任何提示或链接。

Thanks all. 谢谢大家。

Answer 1

You can use the System.Xml.XPath.Extensions class to evaluate XPath expressions on an XDocument. 您可以使用System.Xml.XPath.Extensions类来评估XDocument上的XPath表达式。

http://msdn.microsoft.com/en-us/library/system.xml.xpath.extensions.aspx http://msdn.microsoft.com/en-us/library/system.xml.xpath.extensions.aspx

For example: 例如：

using System.Xml.XPath;
...
XDocument doc = XDocument.Load("sample.xml");
var matching = doc.XPathEvaluate("//Book[@Title='Great Expectations']");  
// 'matching' could be an IEnumerable of XElements, depending on the query

Answer 2

Assuming a simple path, and you just want to add some data at the end of it. 假设一个简单的路径，你只想在它的末尾添加一些数据。

Starting with some example data: 从一些示例数据开始：

var xml = XDocument.Parse(@"<?xml version=""1.0""?>
<messages>
  <request type=""MSG"">
    <header>
      <datestamp>2019-02-26T14:49:41+00:00</datestamp>
      <source>1</source>
    </header>
    <body>
      <title>Hi there</title>
    </body>
  </request>
</messages>
");

This won't work because the product node doesn't exist: 这不起作用，因为产品节点不存在：

xml.XPathSelectElement("/messages/request/body/product")
    ?.Add(new XElement("description", "A new product"));

To do this you could define your own extension method: 为此，您可以定义自己的扩展方法：

public static class extensionMethods
{
    public static XElement FindOrAddElement(this XContainer xml, string nodeName)
    {
        var node = xml.Descendants().FirstOrDefault(x => x.Name == nodeName);
        if (node == null)
            xml.Add(new XElement(nodeName));
        return xml.Descendants().FirstOrDefault(x => x.Name == nodeName);
    }
}

And chain these together to create your new path. 并将这些链接在一起以创建您的新路径。

xml.FindOrAddElement("messages")
   .FindOrAddElement("request")
   .FindOrAddElement("body")
   .FindOrAddElement("product")
   ?.Add(new XElement("description", "A new product"));

使用LINQ-to-XML通过xpath查找或创建元素

问题描述

2 个解决方案

解决方案1
1 2011-01-04 14:44:37

解决方案2
0 2019-03-01 16:01:51

使用LINQ-to-XML通过xpath查找或创建元素

问题描述

2 个解决方案

解决方案1 1 2011-01-04 14:44:37

解决方案2 0 2019-03-01 16:01:51

解决方案1
1 2011-01-04 14:44:37

解决方案2
0 2019-03-01 16:01:51