My.Computer.FileSystem.WriteAllText Method

Visual Basic Language Reference

Writes text to a file.

' Usage
My.Computer.FileSystem.WriteAllText(file ,text ,append)
My.Computer.FileSystem.WriteAllText(file ,text ,append ,encoding)
' Declaration
Public Sub WriteAllText( _
   ByVal file As String, _
   ByVal text As String, _
   ByVal append As Boolean _
)
' -or-
Public Sub WriteAllText( _
   ByVal file As String, _
   ByVal text As String, _
   ByVal append As Boolean, _
   ByVal encoding As System.Text.Encoding _
)

Parameters

file: String. File to be written to. Required.
text: String. Text to be written to file. Required.
append: Boolean. Whether to append text or overwrite existing text. Default is False. Required.
encoding: Encoding. What encoding to use when you write to the file. Required. Default is UTF-8.

Exceptions

The following conditions may cause an exception:

The path is not valid because of one of the following reasons: it is a zero-length string; it contains only white space; it contains invalid characters, ends with a trailing slash, or is a device path (starts with \\.\) (ArgumentException).
The path is not valid because it is Nothing (ArgumentNullException).
file points to a path that does not exist (FileNotFoundException or DirectoryNotFoundException).
The file is being used by another process, or an I/O error occurs (IOException).
The path exceeds the system-defined maximum length (PathTooLongException).
A file or directory name in the path contains a colon (:) or is in an invalid format (NotSupportedException).
The user lacks necessary permissions to view the path (SecurityException).

If you are running in a partial-trust context, the code might throw an exception because of insufficient permissions. For more information, see Code Access Security Basics.

Remarks

When no encoding is specified, UTF-8 is used. The byte order mark (BOM) for the encoding is written to the file unless you specify Encoding..::.Default, which uses the system's current ANSI code page. If the specified encoding does not match the existing encoding of the file, the specified encoding is ignored.

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

If the append parameter is True, the method appends the text to the file; otherwise existing text in the file is overwritten.

Note:
The WriteAllText method opens a file, writes to it, and then closes it. Code that uses the WriteAllText method is simpler than code that uses a StreamWriter object. However, if you are adding strings to a file by using a loop, a StreamWriter object can provide better performance because you only have to open and close the file one time. For more information, see My.Computer.FileSystem.OpenTextFileWriter Method.

Note:

The WriteAllText method opens a file, writes to it, and then closes it. Code that uses the WriteAllText method is simpler than code that uses a StreamWriter object. However, if you are adding strings to a file by using a loop, a StreamWriter object can provide better performance because you only have to open and close the file one time. For more information, see My.Computer.FileSystem.OpenTextFileWriter Method.

Tasks

The following table lists examples of tasks that involve the My.Computer.FileSystem.WriteAllText method.

To	See
Write text to a file	How to: Write Text to Files in Visual Basic
Append text to a file	How to: Append to Text Files in Visual Basic

Example

This example writes the line "This is new text to be added." to the file Test.txt, overwriting any existing text in the file.

Visual Basic

My.Computer.FileSystem.WriteAllText("C:\TestFolder1\test.txt", _
"This is new text to be added.", False)

This example writes the names of the files in the Documents and Settings folder to FileList.txt, inserting a carriage return between each for better readability.

Visual Basic

For Each foundFile As String In _
My.Computer.FileSystem.GetFiles("C:\Documents and Settings")
    foundFile = foundFile & vbCrLf
    My.Computer.FileSystem.WriteAllText _
    ("C:\Documents and Settings\FileList.txt", foundFile, True)
Next

Requirements

Namespace: Microsoft.VisualBasic.MyServices

Class: FileSystemProxy (provides access to FileSystem)

Assembly: Visual Basic Runtime Library (in Microsoft.VisualBasic.dll)

Availability by Project Type

Project type	Available
Windows Application	Yes
Class Library	Yes
Console Application	Yes
Windows Control Library	Yes
Web Control Library	Yes
Windows Service	Yes
Web Site	Yes

Permissions

The following permission may be required:

Permission	Description
FileIOPermission	Controls the ability to access files and folders. Associated enumeration: Unrestricted.

For more information, see Code Access Security and Requesting Permissions.

Reference

My.Computer.FileSystem Object

System.Text..::.Encoding

FileSystem..::.WriteAllText

My.Computer.FileSystem.OpenTextFileWriter Method

Other Resources

Writing to Files in Visual Basic