File and Stream I/O C#

File and stream I/O (input/output) refers to the transfer of data either to or from a storage medium. In the .NET Framework, the System.IO namespaces contain types that enable reading and writing, both synchronously and asynchronously, on data streams and files. These namespaces also contain types that perform compression and decompression on files, and types that enable communication through pipes and serial ports. 

File and Directory:
Here are some commonly used file and directory classes: File - provides static methods for creating, copying, deleting, moving, and opening files, and helps create a FileStream object. FileInfo - provides instance methods for creating, copying, deleting, moving, and opening files, and helps create a FileStream object. Directory - provides static methods for creating, moving, and enumerating through directories and subdirectories. DirectoryInfo - provides instance methods for creating, moving, and enumerating through directories and subdirectories. Path - provides methods and properties for processing directory strings in a cross-platform manner.

Streams :
The abstract base class Stream supports reading and writing bytes. All classes that represent streams inherit from the Stream class. The Stream class and its derived classes provide a common view of data sources and repositories, and isolate the programmer from the specific details of the operating system and underlying devices.

Streams involve three fundamental operations: 
Reading - transferring data from a stream into a data structure, such as an array of bytes. 
Writing - transferring data to a stream from a data source. 
Seeking - querying and modifying the current position within a stream. 

Here are some commonly used stream classes: 
FileStream – for reading and writing to a file.
IsolatedStorageFileStream – for reading and writing to a file in isolated storage.
MemoryStream – for reading and writing to memory as the backing store. BufferedStream – for improving performance of read and write operations. NetworkStream – for reading and writing over network sockets. 
PipeStream – for reading and writing over anonymous and named pipes. CryptoStream – for linking data streams to cryptographic transformations. 


Readers and Writers : The System.IO namespace also provides types for reading encoded characters from streams and writing them to streams. Typically, streams are designed for byte input and output. The reader and writer types handle the conversion of the encoded characters to and from bytes so the stream can complete the operation. Each reader and writer class is associated with a stream, which can be retrieved through the class's BaseStream property.

Here are some commonly used reader and writer classes: 
BinaryReader and BinaryWriter – for reading and writing primitive data types as binary values. 
StreamReader and StreamWriter – for reading and writing characters by using an encoding value to convert the characters to and from bytes. StringReader and StringWriter – for reading and writing characters to and from strings.
TextReader and TextWriter – serve as the abstract base classes for other readers and writers that read and write characters and strings, but not binary data. 

Asynchronous I/O operations : Reading or writing a large amount of data can be resource-intensive. You should perform these tasks asynchronously if your application needs to remain responsive to the user. With synchronous I/O operations, the UI thread is blocked until the resource-intensive operation has completed. Use asynchronous I/O operations when developing Windows Store apps to prevent creating the impression that your app has stopped working. The asynchronous members contain Async in their names, such as the CopyToAsync, FlushAsync, ReadAsync, and WriteAsync methods. You use these methods with the async and await keywords. Compression : Compression refers to the process of reducing the size of a file for storage. Decompression is the process of extracting the contents of a compressed file so they are in a usable format. The System.IO.Compression namespace contains types for compressing and decompressing files and streams. 

The following classes are frequently used when compressing and decompressing files and streams:
ZipArchive – for creating and retrieving entries in the zip archive. ZipArchiveEntry – for representing a compressed file. 
ZipFile – for creating, extracting, and opening a compressed package. ZipFileExtensions – for creating and extracting entries in a compressed package. 
DeflateStream – for compressing and decompressing streams using the Deflate algorithm.
 GZipStream – for compressing and decompressing streams in gzip data format.