.NET & XML

Reading an XmlDocument

An XmlDocument can easily be loaded from disk using the Load( ) method. It has overloads for a Stream, filename, TextReader, or XmlReader, and the LoadXml( ) method will load an XML string from memory. This provides great flexibility; you can load an XmlDocument from a file, a web site, standard input, a memory buffer, or any subclass of Stream or TextReader, as well as any subclass of XmlReader.

For example, suppose the inventory file were stored on a web server, at http://www.angushardware.com/inventory.xml. The following code would let you read it:

XmlDocument document = new XmlDocument( );
document.Load("http://www.angushardware.com/inventory.xml");

After reading the entire document into memory, you now have non-sequential access to the entire XML tree. For example, you could easily navigate down to the number of each item in stock using the XmlNode type’s SelectNodes( ) method. SelectNodes( ) returns an XmlNodeList based on an XPath expression; in this case, you’re selecting all nodes that match the expression //items/item, and writing them to the console:

XmlDocument document = new XmlDocument( );
document.Load("http://www.angushardware.com/inventory.xml"); 
XmlNodeList items = document.SelectNodes("//items/item");
foreach (XmlElement item in items) {
  Console.WriteLine("{0} units of product code {1} in stock",
    item.GetAttribute("quantity"),
    item.GetAttribute("productCode"));
}

Tip

XPath is covered in Chapter 6.

Although you don’t necessarily know in ...