The examples in this chapter use the System.Linq, System.Xml.Linq, and System.Collections.Generic namespaces. Therefore, you should add using directives for these namespaces to your code if they are not already present:
using System.Linq; using System.Xml.Linq; using System.Collections.Generic;
In addition to these namespaces, if you download the companion code, you will see that I also added a using directive for the System.Diagnostics namespace. This will not be necessary if you are typing in the examples from this chapter. It is necessary in the downloadable companion code due to some housekeeping code.