C# Stream:

C# includes following standard IO (Input/Output) classes to read/write from different sources like a file, memory, network, isolated storage, etc.

Stream: System.IO.Stream is an abstract class that provides standard methods to transfer bytes (read, write, etc.) to the source. It is like a wrapper class to transfer bytes. Classes that need to read/write bytes from a particular source must implement the Stream class.

The following classes inherits Stream class to provide functionality to Read/Write bytes from a particular source:

FileStream reads or writes bytes from/to a physical file whether it is a .txt, .exe, .jpg or any other file. FileStream is derived from the Stream class.

MemoryStream: MemoryStream reads or writes bytes that are stored in memory.

BufferedStream: BufferedStream reads or writes bytes from other Streams to improve the performance of certain I/O operations.

NetworkStream: NetworkStream reads or writes bytes from a network socket.

PipeStream: PipeStream reads or writes bytes from different processes.

CryptoStream: CryptoStream is for linking data streams to cryptographic transformations.

The following diagram shows the hierarchy of stream classes:

Readers and Writers:

StreamReader: StreamReader is a helper class for reading characters from a Stream by converting bytes into characters using an encoded value. It can be used to read strings (characters) from different Streams like FileStream, MemoryStream, etc.

StreamWriter: StreamWriter is a helper class for writing a string to a Stream by converting characters into bytes. It can be used to write strings to different Streams such as FileStream, MemoryStream, etc.

BinaryReader: BinaryReader is a helper class for reading primitive datatype from bytes.

BinaryWriter: BinaryWriter writes primitive types in binary.

The above image shows that FileStream reads bytes from a physical file and then StreamReader reads strings by converting those bytes to strings. In the same way, StreamWriter takes a string and converts it into bytes and writes to FileStream and then FileStream writes the bytes to a physical file. So FileStream deals with bytes where as StreamReader & StreamWriter deals with strings.

Points to Remember :

1. Stream is an abstract class for transfering bytes from different sources. It is base class for all other class that reads\writes bytes to different sources.
2. FileStream class provides reading and writing functionality of bytes to physical file.
3. Reader & writer classes provides functionality to read bytes from Stream classes (FileStream, MemoryStream etc) and converts bytes into appropriate encoding.
4. StreamReader provides a helper method to read string from FileStream by converting bytes into strings. StreamWriter provides a helper method to write string to FileStream by converting strings into bytes.

Learn how to read/write to the File system in the next section.