In the framework of .NET, the System.IO namespace is the region of the base class libraries devoted to file-based (and memory-based) input and output (I/O) services. Like any namespace, System.IO defines a set of classes, interfaces, enumerations, structures, and delegates, most of which you can find in mscorlib.dll. In addition to the types contained within mscorlib.dll, the System.dll assembly defines additional members of the System.IO namespace. Note that all Visual Studio 2010 projects automatically set a reference to both assemblies.
Many of the types within the System.IO namespace focus on the programmatic manipulation of physical directories and files. However, additional types provide support to read data from and write data to string buffers, as well as raw memory locations. Table 20-1 outlines the core (non-abstract) classes, providing a road map of the functionality in System.IO.
Table 20-1. Key Members of the System.IO Namespace
| Non-abstract I/O Class Type | Meaning in Life |
|---|---|
| BinaryReader BinaryWriter | These classes allow you to store and retrieve primitive data types (integers, Booleans, strings, and whatnot) as a binary value. |
| BufferedStream | This class provides temporary storage for a stream of bytes that you can commit to storage at a later time. |
| Directory DirectoryInfo | You use these classes to manipulate a machine’s directory structure. The Directory type exposes functionality using static members, while the DirectoryInfo type exposes similar functionality from a valid object reference. |
| DriveInfo | This class provides detailed information regarding the drives that a given machine uses. |
| File FileInfo | You use these classes to manipulate a machine’s set of files. The File type exposes functionality using static members, while the FileInfo type exposes similar functionality from a valid object reference. |
| FileStream | This class gives you random file access (e.g., seeking capabilities) with data represented as a stream of bytes. |
| FileSystemWatcher | This class allows you to monitor the modification of external files in a specified directory. |
| MemoryStream | This class provides random access to streamed data stored in memory rather than a physical file. |
| Path | This class performs operations on System.String types that contain file or directory path information in a platform-neutral manner. |
| StreamWriter StreamReader | You use these classes to store (and retrieve) textual information to (or from) a file. These types do not support random file access. |
| StringWriter StringReader | Like the StreamReader/StreamWriter classes, these classes also work with textual information. However, the underlying storage is a string buffer rather than a physical file. |
In addition to these concrete class types, System.IO defines a number of enumerations, as well as a set of abstract classes (e.g., Stream, TextReader, and TextWriter), that define a shared polymorphic interface to all descendents. You will read about many of these types in this chapter.