C# in a Nutshell, Second Edition

Chapter 31. System.IO

The System.IO types serve as the primary means for stream-oriented I/O—files, principally, although the abstract types defined here serve as base classes for other forms of I/O, such as the XML stack in System.Xml. The System.IO namespace is shown in Figure 31-1 and Figure 31-2.

The System.IO namespace can be seen as two distinct partitions: a set of utility types for using and working with the local machine’s filesystem, and a protocol stack for working with bytestream-oriented input and output. The former partition is the collection of classes such as Directory and FileSystemWatcher, whereas the latter partition is the set of Stream and Reader/Writer types.

The Stream types in System.IO follow a basic object model, similar to the I/O model used by the C/C++ runtime library: all serial byte access is a stream, and there are different sources and sinks for this serialized byte data. In the System.IO package, this is represented directly by the abstract base type Stream; its concrete subtypes represent the actual I/O access: FileStream represents I/O to a file, and MemoryStream represents I/O to a literal array of bytes (whose size is dynamically managed) in memory. Other packages within the .NET Framework Class Library offer up their own Stream-derived types. For example, in the System.Net namespace, socket connections and HTTP responses are offered up as Stream-derived types, giving .NET programmers the ability to treat any sort of input or output data as “just ...