Compose streams

A backing store is a storage medium, such as a disk or memory. Each different backing store implements its own stream as an implementation of the Stream class.

Each stream type reads and writes bytes from and to its given backing store. Streams that connect to backing stores are called base streams. Base streams have constructors with the parameters necessary to connect the stream to the backing store. For example, FileStream has constructors that specify a path parameter, which specifies how the file will be shared by processes.

The design of the System.IO classes provides simplified stream composition. You can attach base streams to one or more pass-through streams that provide the functionality you want. You can attach a reader or writer to the end of the chain, so the preferred types can be read or written easily.

The following code examples create a FileStream around the existing MyFile.txt in order to buffer MyFile.txt. Note that FileStreams are buffered by default.

Important

The examples assume that a file named MyFile.txt already exists in the same folder as the app.

Example: Use StreamReader

The following example creates a StreamReader to read characters from the FileStream, which is passed to the StreamReader as its constructor argument. StreamReader.ReadLine then reads until StreamReader.Peek finds no more characters.

using System;
using System.IO;

public class CompBuf
{
    private const string FILE_NAME = "MyFile.txt";

    public static void Main()
    {
        if (!File.Exists(FILE_NAME))
        {
            Console.WriteLine($"{FILE_NAME} does not exist!");
            return;
        }
        FileStream fsIn = new FileStream(FILE_NAME, FileMode.Open,
            FileAccess.Read, FileShare.Read);
        // Create an instance of StreamReader that can read
        // characters from the FileStream.
        using (StreamReader sr = new StreamReader(fsIn))
        {
            string input;
            // While not at the end of the file, read lines from the file.
            while (sr.Peek() > -1)
            {
                input = sr.ReadLine();
                Console.WriteLine(input);
            }
        }
    }
}
Imports System.IO

Public Class CompBuf
    Private Const FILE_NAME As String = "MyFile.txt"

    Public Shared Sub Main()
        If Not File.Exists(FILE_NAME) Then
            Console.WriteLine($"{FILE_NAME} does not exist!")
            Return
        End If
        Dim fsIn As new FileStream(FILE_NAME, FileMode.Open, _
            FileAccess.Read, FileShare.Read)
        ' Create an instance of StreamReader that can read
        ' characters from the FileStream.
        Using sr As New StreamReader(fsIn)
            Dim input As String
            ' While not at the end of the file, read lines from the file.
            While sr.Peek() > -1
                input = sr.ReadLine()
                Console.WriteLine(input)
            End While
        End Using
    End Sub
End Class

Example: Use BinaryReader

The following example creates a BinaryReader to read bytes from the FileStream, which is passed to the BinaryReader as its constructor argument. ReadByte then reads until PeekChar finds no more bytes.

using System;
using System.IO;

public class ReadBuf
{
    private const string FILE_NAME = "MyFile.txt";

    public static void Main()
    {
        if (!File.Exists(FILE_NAME))
        {
            Console.WriteLine($"{FILE_NAME} does not exist.");
            return;
        }
        FileStream f = new FileStream(FILE_NAME, FileMode.Open,
            FileAccess.Read, FileShare.Read);
        // Create an instance of BinaryReader that can
        // read bytes from the FileStream.
        using (BinaryReader br = new BinaryReader(f))
        {
            byte input;
            // While not at the end of the file, read lines from the file.
            while (br.PeekChar() > -1 )
            {
                input = br.ReadByte();
                Console.WriteLine(input);
            }
        }
    }
}
Imports System.IO

Public Class ReadBuf
    Private Const FILE_NAME As String = "MyFile.txt"

    Public Shared Sub Main()
        If Not File.Exists(FILE_NAME) Then
            Console.WriteLine($"{FILE_NAME} does not exist.")
            Return
        End If
        Dim f As New FileStream(FILE_NAME, FileMode.Open, _
            FileAccess.Read, FileShare.Read)
        ' Create an instance of BinaryReader that can
        ' read bytes from the FileStream.
        Using br As new BinaryReader(f)
            Dim input As Byte
            ' While not at the end of the file, read lines from the file.
            While br.PeekChar() > -1
                input = br.ReadByte()
                Console.WriteLine (input)
            End While
        End Using
    End Sub
End Class

See also