C# 4 and .NET 4

Using XPathnavigators ❘ 917
to this:
//create the declaration section
XmlDeclaration newDec = doc.CreateXmlDeclaration("1.0",null,null);
doc.AppendChild(newDec);
//create the new root element
XmlElement newRoot = doc.CreateElement("newBookstore");
doc.AppendChild(newRoot);
First, you create a new XmlDeclaration. The parameters are the version (always 1.0 for now), the
encoding, and the standalone flag. The encoding parameter should be set to a string that is part of
the System.Text.Encoding class if null is not used (null defaults to UTF-8). The standalone flag
can be either yes, no, or null. If it is null, the attribute is not used and will not be included in the
document.
The next element that is created will become the DocumentElement. In this case, it is called newBookstore
so that you can see the difference. The rest of the code is the same as in the previous example and works in
the same way. This is booksEdit.xml, which is generated from the following code:
The Case of the Missing Cookie
C. Monster
9.95
You will want to use the XmlDocument class when you want to have random access to the document, or the
XmlReader-based classes when you want a streaming-type model instead. Remember that there is a cost
for the flexibility of the XmlNode-based XmlDocument class — memory requirements are higher and the
performance of reading the document is not as good as when using XmlReader. There is another way to
traverse an XML document: the XPathNavigator.
using XPaThnaVigaTors
An XPathNavigator is used to select, iterate through, and sometimes edit data from an XML
document. An XPathNavigator can be created from an XmlDocument to allow editing capabilities or from
an XPathDocument for read-only use. Because the XPathDocument is read-only, it performs very well.
Unlike the XmlReader, the XPathNavigator is not a streaming model, so the same document can be used
without having to re-read and parse.
The XPathNavigaor is part of the System.Xml.XPath namespace. XPath is a query language used to select
specific nodes or elements from an XML document for processing.
The system.Xml.XPath namespace
The System.Xml.XPath namespace is built for speed. It provides a read-only view of your XML
documents, so there are no editing capabilities. Classes in this namespace are built to do fast iteration and
selections on the XML document in a cursory fashion.
The following table lists the key classes in System.Xml.XPath and gives a short description of the purpose
of each class.
www.it-ebooks.info