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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 ()
public void Flush ()
public override function Flush ()
Not applicable.

Exception typeCondition


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.");

// Update the file.
case 'W' : 
    try {
        fileStream.Seek(textLength, SeekOrigin.Begin);
            textLength - 1, byteCount);
        tempString = new String(uniEncoding.GetChars(
            readText, textLength - 1, byteCount));
        recordNumber = Int32.Parse(tempString)+1;
        fileStream.Seek(textLength, SeekOrigin.Begin);
            (new Integer( recordNumber)).ToString()),
            0, byteCount);
        Console.WriteLine("Record has been updated.");

Windows 98, Windows Server 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 Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 2.0, 1.0

XNA Framework

Supported in: 1.0
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