使用LINQ查询XML文件。

I have an XML file that I want to query with LINQ. I want for every record, create a new row. Here is what I have tried up till yet and have failed.

我有一个XML文件，我想用LINQ查询它。我想为每条记录创建一个新的行。这是我到现在还在尝试的，但失败了。

<?xml version="1.0" encoding="utf-8"?>
<categories xmlns="urn:schemas-pi-meta:categories" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="urn:schemas-pi-meta:categories Xsd/meta.xml.config.xsd">
<category name="history">
    <data>
      <value name="customer">2</value>
      <value name="truck">1</value>
    </data>
    <category name="record">
      <data>
        <value name="time">1/3/2013 2:22:41 PM</value>
        <value name="quantity">3</value>
        <value name="unit">barrels</value>
        <value name="cancelled">false</value>
        <value name="errored">false</value>
      </data>
    </category>
  </category>

The file is longer so I have cut it down but it repeats itself.

这个文件比较长，所以我把它剪了下来，但是它自己重复。

This is what I have tried to do:

这就是我想做的:

 XElement root = XElement.Load("D:\\Linq XM\\history.xml.config");

 IEnumerable<XElement> address = from el in root.Elements("categories")
    where (string)el.Attribute("category") == "record"
    select el;

I have tried to change Elements value thinking that I am perhaps missing something but somehow the query isn't returning my data.

我试图改变元素的值，认为我可能遗漏了一些东西，但不知何故，查询并没有返回我的数据。

1 个解决方案

#1

There are four problems as far as I can see.

在我看来，有四个问题。

The first problem is that you're looking for categories elements under the root element - when the categories element is the root element. I suspect you really want to be looking for category elements rather than categories elements.

第一个问题是在根元素下查找类别元素——当categories元素是根元素时。我怀疑你真的想要寻找类别元素而不是类别元素。

The second problem is that you're trying to find an attribute named category. It looks to me like you should be checking for an attribute named name within elements called category.

第二个问题是您试图找到一个名为category的属性。在我看来，您应该在名为category的元素中检查名为name的属性。

The third problem is that the category with a name attribute of record isn't actually a direct child element of categories at all - it's a descendant, but not a direct child - so you should use Descendants instead of Elements.

第三个问题是，带有name属性的category实际上根本不是category的直接子元素——它是子类，而不是直接子类——所以应该使用子类而不是元素。

The fourth problem is that you're not specifying a namespace. This part of the file:

第四个问题是您没有指定名称空间。文件的这一部分:

<categories xmlns="urn:schemas-pi-meta:categories"  ...

specifies that the default namespace for this element and descendants is the URI "urn:schemas-pi-meta:categories". So you need to specify that when you say what you're looking for.

指定该元素及其后代的默认名称空间是URI“urn:schemas-pi-meta:categories”。所以当你说你要找的东西时，你需要明确这一点。

Putting these all together, you'd get:

把这些放在一起，你会得到:

XNamespace ns = "urn:schemas-pi-meta:categories";
var query = from el in root.Descendants(ns + "category")
            where (string) el.Attribute("name") == "record"
            select el;

Or without a query expression (as it's more hassle than it's worth here):

或者没有查询表达式(因为它比这里的值更麻烦):

XNamespace ns = "urn:schemas-pi-meta:categories";
var query = root.Descendants(ns + "category")
                .Where(el => (string) el.Attribute("name") == "record");

#1