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FileStream.Read Method

Reads a block of bytes from the stream and writes the data in a given buffer.

Namespace: System.IO
Assembly: mscorlib (in mscorlib.dll)

public override int Read (
	[InAttribute] [OutAttribute] byte[] array,
	int offset,
	int count
)
public int Read (
	/** @attribute InAttribute() */ /** @attribute OutAttribute() */ byte[] array, 
	int offset, 
	int count
)
public override function Read (
	array : byte[], 
	offset : int, 
	count : int
) : int

Parameters

array

When this method returns, contains the specified byte array with the values between offset and (offset + count - 1) replaced by the bytes read from the current source.

offset

The byte offset in array at which to begin reading.

count

The maximum number of bytes to read.

Return Value

The total number of bytes read into the buffer. This might be less than the number of bytes requested if that number of bytes are not currently available, or zero if the end of the stream is reached.

Exception typeCondition

ArgumentNullException

array is a null reference (Nothing in Visual Basic).

ArgumentOutOfRangeException

offset or count is negative.

NotSupportedException

The stream does not support reading.

IOException

An I/O error occurs.

ArgumentException

offset and count describe an invalid range in array.

ObjectDisposedException

Methods were called after the stream was closed.

This method overrides Read.

The offset parameter gives the offset of the byte in array (the buffer index) at which to begin reading, and the count parameter gives the maximum number of bytes to be read from this stream. The returned value is the actual number of bytes read, or zero if the end of the stream is reached. If the read operation is successful, the current position of the stream is advanced by the number of bytes read. If an exception occurs, the current position of the stream is unchanged.

The Read method returns zero only after reaching the end of the stream. Otherwise, Read always reads at least one byte from the stream before returning. If no data is available from the stream upon a call to Read, the method will block until at least one byte of data can be returned. An implementation is free to return fewer bytes than requested even if the end of the stream has not been reached.

Use BinaryReader for reading primitive data types.

The following table lists examples of other typical or related I/O tasks.

To do this...

See the example in this topic...

Create a text file.

How to: Write Text to a File

Write to a text file.

How to: Write Text to a File

Read from a text file.

How to: Read Text from a File

Append text to a file.

How to: Open and Append to a Log File

File.AppendText

FileInfo.AppendText

Rename or move a file.

File.Move

FileInfo.MoveTo

Copy a file.

File.Copy

FileInfo.CopyTo

Get the size of a file.

FileInfo.Length

Get the attributes of a file.

File.GetAttributes

Set the attributes of a file.

File.SetAttributes

Determine if a file exists.

File.Exists

Read from a binary file.

How to: Read and Write to a Newly Created Data File

Write to a binary file.

How to: Read and Write to a Newly Created Data File

Create a directory.

Directory.CreateDirectory

Directory.CreateDirectory

The following example demonstrates reading a specified number of bytes from an existing file.

using System;
using System.IO;

class FSRead
{
    public static void Main()
    {
        //Create a file stream from an existing file.
        FileInfo fi=new FileInfo("c:\\csc.txt");       
        FileStream fs=fi.OpenRead();
        
        //Read 100 bytes into an array from the specified file.
        int nBytes=100;
        byte[] ByteArray=new byte[nBytes];
        int nBytesRead=fs.Read(ByteArray, 0, nBytes);
        Console.WriteLine("{0} bytes have been read from the specified file.", nBytesRead.ToString());
    }
}

import System.*;
import System.IO.*;

class FSRead
{
    public static void main(String[] args)
    {
        //Create a file stream from an existing file.
        FileInfo fi = new FileInfo("c:\\csc.txt");
        FileStream fs = fi.OpenRead();

        //Read 100 bytes into an array from the specified file.
        int nBytes = 100;
        ubyte byteArray[] = new ubyte[nBytes];
        int nBytesRead = fs.Read(byteArray, 0, nBytes);
        Console.WriteLine("{0} bytes have been read from the specified file.",
            ((Int32)nBytesRead).ToString());
    } //main
} //FSRead

Windows 98, Windows 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see System Requirements.

.NET Framework

Supported in: 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 2.0, 1.0

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