File.AppendAllText Method

Reference

Definition

Namespace:: System.IO

Assemblies:: netstandard.dll, System.Runtime.dll

Assemblies:: mscorlib.dll, System.IO.FileSystem.dll

Assemblies:: netstandard.dll, System.IO.FileSystem.dll

Assemblies:: netstandard.dll, System.IO.FileSystem.dll, System.Runtime.dll

Assembly:: System.IO.FileSystem.dll

Assembly:: mscorlib.dll

Assembly:: netstandard.dll

Important

Some information relates to prerelease product that may be substantially modified before it’s released. Microsoft makes no warranties, express or implied, with respect to the information provided here.

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

Overloads

AppendAllText(String, ReadOnlySpan<Char>)	Appends the specified string to the file, creating the file if it does not already exist.
AppendAllText(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.
AppendAllText(String, ReadOnlySpan<Char>, Encoding)	Appends the specified string to the file, creating the file if it does not already exist.
AppendAllText(String, String, Encoding)	Appends the specified string to the file using the specified encoding, creating the file if it does not already exist.

AppendAllText(String, ReadOnlySpan<Char>)

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

public:
 static void AppendAllText(System::String ^ path, ReadOnlySpan<char> contents);

public static void AppendAllText(string path, ReadOnlySpan<char> contents);

static member AppendAllText : string * ReadOnlySpan<char> -> unit

Public Shared Sub AppendAllText (path As String, contents As ReadOnlySpan(Of Char))

Parameters

path: String

The file to append to.

contents: ReadOnlySpan<Char>

The characters to write to the file.

Exceptions

ArgumentNullException

path is null.

ArgumentException

path is empty.

PathTooLongException

The specified path, file name, or both exceed the system-defined maximum length.

DirectoryNotFoundException

The specified path is invalid (for example, 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-

path specified a file that is hidden.

-or-

path specified a directory.

-or-

The caller does not have the required permission.

-or-

This operation is not supported on the current platform.

NotSupportedException

path is in an invalid format.

Remarks

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.

Applies to

.NET 10 and .NET 9

Product	Versions
.NET	9, 10

AppendAllText(String, String)

Source:: File.cs

Source:: File.cs

Source:: File.cs

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.

public:
 static void AppendAllText(System::String ^ path, System::String ^ contents);

public static void AppendAllText(string path, string contents);

public static void AppendAllText(string path, string? contents);

static member AppendAllText : string * string -> unit

Public Shared Sub AppendAllText (path As String, contents As String)

Parameters

path: String

The file to append the specified string to.

contents: String

The string to append to the file.

Exceptions

ArgumentException

.NET Framework and .NET Core versions older than 2.1: path is a zero-length string, contains only white space, or contains one or more invalid characters. You can query for invalid characters by using the GetInvalidPathChars() method.

ArgumentNullException

path is null.

PathTooLongException

The specified path, file name, or both exceed the system-defined maximum length.

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.

Examples

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);
        }

        // 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);
        Console.WriteLine(readText);
    }
}

open System
open System.IO

let path = @"c:\temp\MyTest.txt"

// This text is added only once to the file.
if File.Exists path |> not then
    // Create a file to write to.
    let 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.
let appendText =
    "This is extra text" + Environment.NewLine

File.AppendAllText(path, appendText)

// Open the file to read from.
let readText = File.ReadAllText path
printfn $"{readText}"

Imports System.IO
Imports System.Text

Public Class Test
    Public Shared Sub Main()
        Dim path As String = "c:\temp\MyTest.txt"

        ' 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)
        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)

        ' Open the file to read from.
        Dim readText As String = File.ReadAllText(path)
        Console.WriteLine(readText)
    End Sub
End Class

Remarks

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 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.

Applies to

.NET 10 and other versions

Product	Versions
.NET	Core 1.0, Core 1.1, Core 2.0, Core 2.1, Core 2.2, Core 3.0, Core 3.1, 5, 6, 7, 8, 9, 10
.NET Framework	2.0, 3.0, 3.5, 4.0, 4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1
.NET Standard	1.3, 1.4, 1.6, 2.0, 2.1
UWP	10.0

AppendAllText(String, ReadOnlySpan<Char>, Encoding)

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

public:
 static void AppendAllText(System::String ^ path, ReadOnlySpan<char> contents, System::Text::Encoding ^ encoding);

public static void AppendAllText(string path, ReadOnlySpan<char> contents, System.Text.Encoding encoding);

static member AppendAllText : string * ReadOnlySpan<char> * System.Text.Encoding -> unit

Public Shared Sub AppendAllText (path As String, contents As ReadOnlySpan(Of Char), encoding As Encoding)

Parameters

path: String

The file to append to.

contents: ReadOnlySpan<Char>

The characters to write to the file.

encoding: Encoding

The encoding to apply to the string.

Exceptions

ArgumentNullException

path or encoding is null.

ArgumentException

path is empty.

PathTooLongException

The specified path, file name, or both exceed the system-defined maximum length.

DirectoryNotFoundException

The specified path is invalid (for example, 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-

path specified a file that is hidden.

-or-

path specified a directory.

-or-

The caller does not have the required permission.

-or-

This operation is not supported on the current platform.

NotSupportedException

path is in an invalid format.

Remarks

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.

Applies to

.NET 10 and .NET 9

Product	Versions
.NET	9, 10

AppendAllText(String, String, Encoding)

Source:: File.cs

Source:: File.cs

Source:: File.cs

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

public:
 static void AppendAllText(System::String ^ path, System::String ^ contents, System::Text::Encoding ^ encoding);

public static void AppendAllText(string path, string contents, System.Text.Encoding encoding);

public static void AppendAllText(string path, string? contents, System.Text.Encoding encoding);

static member AppendAllText : string * string * System.Text.Encoding -> unit

Public Shared Sub AppendAllText (path As String, contents As String, encoding As Encoding)

Parameters

path: String

The file to append the specified string to.

contents: String

The string to append to the file.

encoding: Encoding

The character encoding to use.

Exceptions

ArgumentException

ArgumentNullException

path is null.

PathTooLongException

The specified path, file name, or both exceed the system-defined maximum length.

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.

Examples

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);
        Console.WriteLine(readText);
    }
}

open System
open System.IO
open System.Text

let path = @"c:\temp\MyTest.txt"

// This text is added only once to the file.
if File.Exists path |> not then
    // Create a file to write to.
    let 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.
let appendText =
    "This is extra text" + Environment.NewLine

File.AppendAllText(path, appendText, Encoding.UTF8)

// Open the file to read from.
let readText = File.ReadAllText path
printfn $"{readText}"

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

Remarks

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.

Applies to

.NET 10 and other versions

Product	Versions
.NET	Core 1.0, Core 1.1, Core 2.0, Core 2.1, Core 2.2, Core 3.0, Core 3.1, 5, 6, 7, 8, 9, 10
.NET Framework	2.0, 3.0, 3.5, 4.0, 4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1
.NET Standard	1.3, 1.4, 1.6, 2.0, 2.1
UWP	10.0

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File.AppendAllText Method

Definition

Overloads

AppendAllText(String, ReadOnlySpan<Char>)

Parameters

Exceptions

Remarks

Applies to

AppendAllText(String, String)

Parameters

Exceptions

Examples

Remarks

Applies to

AppendAllText(String, ReadOnlySpan<Char>, Encoding)

Parameters

Exceptions

Remarks

Applies to

AppendAllText(String, String, Encoding)

Parameters

Exceptions

Examples

Remarks

Applies to

Additional resources