C# 4 and .NET 4

summary ❘ 953
In this case, the first instance of the element is overwritten with the value of Bill Evjen, king
of Denmark using the SetValue() method of the Element() object. After the SetValue() is called and the
value is applied to the XML document, the value is then retrieved using the same approach as before. When
you run this bit of code, you can indeed see that the value of the first element has been changed.
Another way to change the document (by adding items to it in this example) is to create the elements you
want as XElement objects and then add them to the document:
using System;
using System.Linq;
using System.Xml.Linq;
namespace ConsoleApplication1
{
class Class1
{
static void Main()
{
XDocument xdoc = XDocument.Load(@"C:\hamlet.xml");
XElement xe = new XElement("PERSONA",
"Bill Evjen, king of Denmark");
xdoc.Element("PLAY").Element("PERSONAE").Add(xe);
var query = from people in xdoc.Descendants("PERSONA")
select people.Value;
Console.WriteLine("{0} Players Found", query.Count());
Console.WriteLine();
foreach (var item in query)
{
Console.WriteLine(item);
}
}
}
}
Console.ReadLine();
code download ConsoleApplication1.sln
In this case, an XElement document is created called xe. The construction of xe will give you the following
XML output:
Bill Evjen, king of Denmark
Then using the Element().Add() method from the XDocument object, you are able to add the created element:
xdoc.Element("PLAY").Element("PERSONAE").Add(xe);
Now when you query all the players, you will find that instead of 26 as before, you now have 27 with the
new one at the bottom of the list. In addition to Add(), you can also use AddFirst(), which will do what it
says — add it to the beginning of the list instead of the end (which is the default).
summary
In this chapter, you explored many aspects of the System.Xml namespace of the .NET Framework. You
looked at how to read and write XML documents using the very fast XmlReader- and XmlWriter-based
classes. You looked at how the DOM is implemented in .NET and how to use the power of DOM. You saw
that XML and ADO.NET are indeed very closely related. A DataSet and an XML document are just two
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