File.AppendAllText Method (String, String, Encoding)
Appends the specified string to the file, creating the file if it does not already exist.
Assembly: mscorlib (in mscorlib.dll)
Public Shared Sub AppendAllText ( path As String, contents As String, encoding As Encoding )
Parameters
- path
-
Type:
System.String
The file to append the specified string to.
- contents
-
Type:
System.String
The string to append to the file.
- encoding
-
Type:
System.Text.Encoding
The character encoding to use.
| Exception | Condition |
|---|---|
| ArgumentException | path is a zero-length string, contains only white space, or contains one or more invalid characters as defined by InvalidPathChars. |
| ArgumentNullException | path is null. |
| PathTooLongException | The specified path, file name, or both exceed the system-defined maximum length. For example, on Windows-based platforms, paths must be less than 248 characters, and file names must be less than 260 characters. |
| DirectoryNotFoundException | The specified path is invalid (for example, the directory doesn’t exist or it is on an unmapped drive). |
| IOException | An I/O error occurred while opening the file. |
| UnauthorizedAccessException | path specified a file that is read-only. -or- This operation is not supported on the current platform. -or- path specified a directory. -or- The caller does not have the required permission. |
| NotSupportedException | path is in an invalid format. |
| SecurityException | The caller does not have the required permission. |
Given a string and a file path, this method opens the specified file, appends the string to the end of the file using the specified encoding, and then closes the file. The file handle is guaranteed to be closed by this method, even if exceptions are raised.
The method creates the file if it doesn’t exist, but it doesn't create new directories. Therefore, the value of the path parameter must contain existing directories.
The following code example demonstrates the use of the AppendAllText method to add extra text to the end of a file. In this example, a file is created if it doesn't already exist, and text is added to it. However, the directory named temp on drive C must exist for the example to complete successfully.
Imports System Imports System.IO Imports System.Text Public Class Test Public Shared Sub Main() Dim path As String = "c:\temp\MyTest.txt" Dim sw As StreamWriter ' This text is added only once to the file. If File.Exists(path) = False Then ' Create a file to write to. Dim createText As String = "Hello and Welcome" + Environment.NewLine File.WriteAllText(path, createText, Encoding.UTF8) End If ' This text is always added, making the file longer over time ' if it is not deleted. Dim appendText As String = "This is extra text" + Environment.NewLine File.AppendAllText(path, appendText, Encoding.UTF8) ' Open the file to read from. Dim readText As String = File.ReadAllText(path) Console.WriteLine(readText) End Sub End Class
for access to write to a file or directory. Associated enumeration: FileIOPermissionAccess.Append
Available since 10
.NET Framework
Available since 2.0
Silverlight
Available since 4.0