Querying an XML File using LINQ

Question

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.

<?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.

This is what I have tried to do:

 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.

Answer 1

There are four problems as far as I can see.

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.

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 .

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 .

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

<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.

Putting these all together, you'd get:

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):

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