How to: Append to Text Files in Visual Basic

The WriteAllText method can be used to append to a text file by specifying that the append parameter is set to True.

To append to a text file

• Use the WriteAllText method, specifying the target file and string to be appended and setting the append parameter to True.

  This example writes the string "This is a test string." to the file named Testfile.txt.

  Dim inputString As String = "This is a test string."
  My.Computer.FileSystem.WriteAllText(
    "C://testfile.txt", inputString, True)
  

Robust Programming

The following conditions may cause an exception:

• 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 \\.\) (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 in use 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).

See also

• WriteAllText
• FileSystem
• Writing to Files