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File.AppendText Method

Creates a StreamWriter that appends UTF-8 encoded text to an existing file.

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

public static StreamWriter AppendText (
	string path
)
public static StreamWriter AppendText (
	String path
)
public static function AppendText (
	path : String
) : StreamWriter
Not applicable.

Parameters

path

The path to the file to append to.

Return Value

A StreamWriter that appends UTF-8 encoded text to an existing file.

Exception typeCondition

UnauthorizedAccessException

The caller does not have the required permission.

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 a null reference (Nothing in Visual Basic).

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, it is on an unmapped drive).

NotSupportedException

path is in an invalid format.

This method is equivalent to the StreamWriter(String,Boolean) constructor overload. If the file specified by path does not exist, it is created. If the file does exist, write operations to the StreamWriter append text to the file. Additional threads are permitted to read the file while it is open.

The path parameter is permitted to specify relative or absolute path information. Relative path information is interpreted as relative to the current working directory. To obtain the current working directory, see GetCurrentDirectory.

The path parameter is not case-sensitive.

For a list of common I/O tasks, see Common I/O Tasks.

The following example appends text to a file.

using System;
using System.IO;

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.
            using (StreamWriter sw = File.CreateText(path)) 
            {
                sw.WriteLine("Hello");
                sw.WriteLine("And");
                sw.WriteLine("Welcome");
            }	
        }

        // This text is always added, making the file longer over time
        // if it is not deleted.
        using (StreamWriter sw = File.AppendText(path)) 
        {
            sw.WriteLine("This");
            sw.WriteLine("is Extra");
            sw.WriteLine("Text");
        }	

        // Open the file to read from.
        using (StreamReader sr = File.OpenText(path)) 
        {
            string s = "";
            while ((s = sr.ReadLine()) != null) 
            {
                Console.WriteLine(s);
            }
        }
    }
}

import System.*;
import System.IO.*;

class Test
{
    public static void main(String[] args)
    {
        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.
            StreamWriter sw = File.CreateText(path);
            try {
                sw.WriteLine("Hello");
                sw.WriteLine("And");
                sw.WriteLine("Welcome");
            }
            finally {
                sw.Dispose();
            }
        }

        // This text is always added, making the file longer over time
        // if it is not deleted.
        StreamWriter sw = File.AppendText(path);
        try {
            sw.WriteLine("This");
            sw.WriteLine("is Extra");
            sw.WriteLine("Text");
        }
        finally {
            sw.Dispose();
        }

        // Open the file to read from.
        StreamReader sr = File.OpenText(path);
        try {
            String s = "";
            while ((s = sr.ReadLine())!= null) {
                Console.WriteLine(s);
            }
        }
        finally {
            sr.Dispose();
        }
    } //main
} //Test

Windows 98, Windows Server 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, 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, 1.1, 1.0

.NET Compact Framework

Supported in: 2.0, 1.0

XNA Framework

Supported in: 1.0

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