When people think of having to store data for their applications, a database such as SQL Server immediately comes to mind. However, XML files are very handy for storing data without the overhead of a database. Using XML files to cache often-used, but seldom changed data such as US state codes, Country code, employee types and other validation tables can avoid network round-trips to a database, and potentially speed up your application. In addition, XML files are great for off-line applications where a user needs to add, edit and delete data when they can't connect to a database. To take advantage of XML within your application, you should use LINQ to XML. I am sure you have used LINQ to iterate over other types of collections. LINQ works great to iterate over XML, too. In this blog post you will use LINQ to XML to read state codes from an XML file and display those values on a web page.)
All too often I see people using switch/Select Case statements when using a Factory pattern. The problem with this is if you wish to add the ability to instantiate a new class in your Factory, you need to add a new 'case' statement, re-compile the code and redeploy that DLL back out to your client machines, or your server(s). Another way to implement a Factory pattern is to use Reflection and Interfaces to dynamically create an instance of a class. This blog post will show you how to use an XML file, an Interface and the Assembly class to dynamically load a list of assemblies and classes to load into an application at runtime.)
In previous blog posts I have discussed how to use XML files to store data in your applications. I showed you how to read those XML files from your project and get XML from a WCF service. One of the problems with reading XML files is when elements or attributes are missing. If you try to read that missing data, then a null value is returned. This can cause a problem if you are trying to load that data into an object and a null is read. This blog post will show you how to create extension methods to detect null values and return valid values to load into your object.)