This documentation is archived and is not being maintained.

FileStream.Flush Method

Clears all buffers for this stream and causes any buffered data to be written to the file system.

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

public override void Flush()


An I/O error occurs.


The stream is closed.

This method overrides Flush.

Flushing the stream will not flush its underlying encoder unless you explicitly call Flush or Close. Setting AutoFlush to true means that data will be flushed from the buffer to the stream, but the encoder state will not be flushed. This allows the encoder to keep its state (partial characters) so that it can encode the next block of characters correctly. This scenario affects UTF8 and UTF7 where certain characters can only be encoded after the encoder receives the adjacent character or characters.

Because a buffer can be used for either reading or writing, Flush performs the following two functions:

  1. Any data previously written to the buffer is copied to the file and the buffer is cleared except for its encoder state.

  2. If CanSeek is true and data was previously copied from the file to the buffer for reading, the current position within the file is decremented by the number of unread bytes in the buffer. The buffer is then cleared.

This code example is part of a larger example provided for the Lock method.

// Update the file. 
case 'W':
            readText, textLength - 1, byteCount);
        tempString = new String(
            readText, textLength - 1, byteCount));
        recordNumber = int.Parse(tempString) + 1;
            textLength, SeekOrigin.Begin);
            0, byteCount);
            "Record has been updated.");

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC, Xbox 360, Zune

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

.NET Framework

Supported in: 3.5, 3.0, 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 3.5, 2.0, 1.0

XNA Framework

Supported in: 3.0, 2.0, 1.0