AppendAllText Method (String, String, Encoding)

File.AppendAllText Method (String, String, Encoding)


Appends the specified string to the file, creating the file if it does not already exist.

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

public static void AppendAllText(
	string path,
	string contents,
	Encoding encoding


Type: System.String

The file to append the specified string to.

Type: System.String

The string to append to the file.

Type: System.Text.Encoding

The character encoding to use.

Exception Condition

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


path is null.


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, the directory doesn’t exist or 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.


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 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.

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, Encoding.UTF8);

        // 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, Encoding.UTF8);

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

for access to write to a file or directory. Associated enumeration: FileIOPermissionAccess.Append

Universal Windows Platform
Available since 10
.NET Framework
Available since 2.0
Available since 4.0
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