File.AppendAllText Method (String, String)

Opens a file, appends the specified string to the file, and then closes the file. If the file does not exist, this method creates a file, writes the specified string to the file, then closes the file.

Namespace: System.IO
Assembly: mscorlib (in mscorlib.dll)

public static void AppendAllText (
	string path,
	string contents
public static void AppendAllText (
	String path, 
	String contents
public static function AppendAllText (
	path : String, 
	contents : String
Not applicable.



The file to append the specified string to.


The string to append to the file.

Exception typeCondition


path is a zero-length string, contains only white space, or contains one or more invalid characters as defined by InvalidPathChars.


path is a null reference (Nothing in Visual Basic).


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.


The specified path is invalid (for example, it is on an unmapped drive).


An I/O error occurred while opening the file.


path specified a file that is read-only.


This operation is not supported on the current platform.


path specified a directory.


The caller does not have the required permission.


The file specified in path was not found.


path is in an invalid format.


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, and then closes the file. The file handle is guaranteed to be closed by this method, even if exceptions are raised.

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.

using System;
using System.IO;
using System.Text;

class Test
    public static void Main()
        string path = @"c:\temp\MyTest.txt";

        // This text is added only once to the file.
        if (!File.Exists(path))
            // Create a file to write to.
            string createText = "Hello and Welcome" + Environment.NewLine;
            File.WriteAllText(path, createText);

        // This text is always added, making the file longer over time
        // if it is not deleted.
        string appendText = "This is extra text" + Environment.NewLine;
        File.AppendAllText(path, appendText);

        // Open the file to read from.
        string readText = File.ReadAllText(path);

Windows 98, Windows Server 2000 SP4, Windows Millennium Edition, 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