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FileSystem.WriteAllBytes Method

Writes data to a binary file.

Namespace:  Microsoft.VisualBasic.FileIO
Assembly:  Microsoft.VisualBasic (in Microsoft.VisualBasic.dll)

public static void WriteAllBytes(
	string file,
	byte[] data,
	bool append


Type: System.String
Path and name of the file to be written to.
Type: System.Byte[]
Data to be written to the file.
Type: System.Boolean
True to append to the file contents; False to overwrite the file contents. Default is False.


The path is not valid for one of the following reasons: it is a zero-length string; it contains only white space; it contains invalid characters; or it is a device path (starts with \\.\); it ends with a trailing slash.


file is Nothing.


The file does not exist.


The file is in use by another process, or an I/O error occurs.


The path exceeds the system-defined maximum length.


A file or directory name in the path contains a colon (:) or is in an invalid format.


There is not enough memory to write the string to buffer.


The user lacks necessary permissions to view the path.

If the specified path, excluding the file name, is not valid, a DirectoryNotFoundException exception will be thrown. If the path is valid but the file does not exist, the file is created.


The WriteAllBytes method opens a file, writes to it, and then closes it. Code that uses the WriteAllBytes method is simpler than code that uses a BinaryWriter object. However, if you are adding data to a file using a loop, a BinaryWriter object can provide better performance because you only have to open and close the file once.

The following table lists an example of a task involving the My.Computer.FileSystem.WriteAllBytes method.

This example appends the data array CustomerData to the file CollectedData.

  "C:\MyDocuments\CustomerData", CustomerData, True)

.NET Framework

Supported in: 4, 3.5, 3.0, 2.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

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