The Directory class is in the System.IO namespace.
Directories in the file system are referenced by Path Strings.
You can look at the MSDN documentation for a wide variety of functions in the
Directory class including ones to list all the files in a directory
or to check if a path string represents an actual directory.
We will generally access operating system files using the Stream abstraction,
discussed earlier in this chapter.
There is also a File class in the System.IO namespace, with a number
of specialized and convenience functions.
We already used the File.Exists function.
You can look at the MSDN documentation for other uses of the File class.