Dropdown bind through xml

XmlDocument xml = new XmlDocument();
string s =Server.MapPath("XMLfILE.xml");
string list = "/catalog/book";
xml.Load(s);
XmlNodeList xn = xml.SelectNodes(list);
foreach (XmlNode eleSourceNode in xn)
{
string ID = eleSourceNode.Attributes["id"].Value;
string author1 = eleSourceNode["author"].InnerText;
DRPLIST.Items.Add(new ListItem(author1 ,ID));
}


//XMLFILE.xml

?xml version="1.0"?>
catalog>
book id="bk101">
author>Gambardella, Matthew /author>
title>XML Developer's Guide /title>
genre>Computer /genre>
price>44.95 /price>
publish_date>2000-10-01 /publish_date>
description>
An in-depth look at creating applications
with XML.
/description>
/book>

book id="bk111">
author>O'Brien, Tim /author>
title>MSXML3: A Comprehensive Guide /title>
genre>Computer /genre>
price>36.95 /price>
publish_date>2000-12-01/publish_date>
description>
The Microsoft MSXML3 parser is covered in
detail, with attention to XML DOM interfaces, XSLT processing,
SAX and more.
/description>
/book>
book id="bk112">
author>Galos, Mike/author>
title>Visual Studio 7: A Comprehensive Guide/title>
genre>Computer /genre>
price>49.95 /price>
publish_date>2001-04-16/publish_date>
description>
Microsoft Visual Studio 7 is explored in depth,
looking at how Visual Basic, Visual C++, C#, and ASP+ are
integrated into a comprehensive development
environment.
/description>
/book>
/catalog>

Link for Asp.net Architecture(Isapi.dll,httpcontext,hpptmodule)

http://www.west-wind.com/presentations/howaspnetworks/howaspnetworks.asp

Boxing and Unboxing(Convert value type to ref type and ref type to value type.)

int Val = 1;
Object Obj = Val; //Boxing
int i = (int)Val; //Unboxing