XML

Namespace

• If namespace isn’t correct,the SelectSingleNode will return null!
• If prefix has specified in xmlns,just like: xmlns:prefix_foo=”name-of-namespace”,all element under the namespace must specify this prefix explicitly. For example

<prefix_foo:book />

• Default Namespaces ( xmlns without prefix,for example: xmlns=”name-of-namespace” ): Defining a default namespace for an element saves us from using prefixes in all the child elements.
• Namespace also can be empty.

Specify a note that contains a value

// Get the note that which value is 'Atwood',using [] to filter the notes.
     note = root.SelectSingleNode("/root/subnote[subsubnote='Atwood']/subsubnote");

Read Value Note

XmlNode.InnerText

Test XML file

<?xml version='1.0'?>
<bookstore xmlns="urn:newbooks-schema">
  <book genre="novel" style="hardcover">
    <title>The Handmaid's Tale</title>
    <author>
      <first-name>Margaret</first-name>
      <last-name>Atwood</last-name>
    </author>
    <price>19.95</price>
  </book>
  <book genre="novel" style="other">
    <title>The Poisonwood Bible</title>
    <author>
      <first-name>Barbara</first-name>
      <last-name>Kingsolver</last-name>
    </author>
    <price>11.99</price>
  </book>
</bookstore>

Test Code

using System;
using System.IO;
using System.Xml;

public class Sample
{
  public static void Main()
  {

      XmlDocument doc = new XmlDocument();
      doc.Load("newbooks.xml");

      // Create an XmlNamespaceManager to resolve the default namespace.
      XmlNamespaceManager nsmgr = new XmlNamespaceManager(doc.NameTable);
      nsmgr.AddNamespace("bk","urn:newbooks-schema");

      // Select the first book written by an author whose last name is Atwood.
      XmlNode book;
      XmlElement root = doc.DocumentElement;
      book = root.SelectSingleNode("descendant::bk:book[bk:author/bk:last-name='Atwood']",nsmgr);

      Console.WriteLine(book.OuterXml);
  }
}

Reference Document

• https://msdn.microsoft.com/en-us/library/ms256471(v=vs.110).aspx
• https://en.wikipedia.org/wiki/XPath
• https://en.wikipedia.org/wiki/XML