The System.IO namespace contains a collection of classes that allow us to do file manipulation in C#. It includes classes that allow us to do operations such as the following:

• Read data from a file
• Write data to a file
• Create/delete new files

At different points during this chapter, through code examples, we will look at all of these I/O operations that we can perform on a file. However, before we start looking at those examples, we need to understand a very important concept, Stream, on which I/O operations are based. 

A stream signifies a sequence of bytes exchanged between applications during an I/O operation. In C#, it's represented by an abstract class called System.IO.Stream. It provides a wrapper class to transfer bytes, and all classes that need to read/write bytes from any source must inherit from this particular class.

Before we move on to learn more about streams and how we deal with it them in C#, let's first look at how we deal with drives, directories, and some other basic operations with files.