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File.AppendText Method

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

[Visual Basic]
Public Shared Function AppendText( _
   ByVal path As String _
) As StreamWriter
[C#]
public static StreamWriter AppendText(
 string path
);
[C++]
public: static StreamWriter* AppendText(
 String* path
);
[JScript]
public static function AppendText(
   path : String
) : StreamWriter;

Parameters

path
The path to the file to append to.

Return Value

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

Exceptions

Exception Type Condition
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, such as being on an unmapped drive.
NotSupportedException path is in an invalid format.

Remarks

This method is equivalent to StreamWriter(String, Boolean). 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 an example of using this method, see the Example section below. The following table lists examples of other typical or related I/O tasks.

To do this... See the example in this topic...
Create a text file. Writing Text to a File
Write to a text file. Writing Text to a File
Read from a text file. Reading Text from a File

Example

[Visual Basic, C#, C++] The following example appends text to a file.

[Visual Basic] 
Imports System
Imports System.IO

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.
            sw = File.CreateText(path)

            sw.WriteLine("Hello")
            sw.WriteLine("And")
            sw.WriteLine("Welcome")
            sw.Flush()
            sw.Close()
        End If

        ' This text is always added, making the file longer over time
        ' if it is not deleted.
        sw = File.AppendText(path)
        sw.WriteLine("This")
        sw.WriteLine("is Extra")
        sw.WriteLine("Text")
        sw.Flush()
        sw.Close()

        ' Open the file to read from.
        Dim sr As StreamReader = File.OpenText(path)
        Dim s As String
        Do While sr.Peek() >= 0
            s = sr.ReadLine()
            Console.WriteLine(s)
        Loop
        sr.Close()
    End Sub
End Class

[C#] 
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);
            }
        }
    }
}

[C++] 
#using <mscorlib.dll>

using namespace System;
using namespace System::IO;

int main() {
    String* path = S"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(S"Hello");
            sw->WriteLine(S"And");
            sw->WriteLine(S"Welcome");
        } __finally {
            if (sw) __try_cast<IDisposable*>(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(S"This");
        sw->WriteLine(S"is Extra");
        sw->WriteLine(S"Text");
    } __finally {
        if (sw) __try_cast<IDisposable*>(sw)->Dispose();
    }

    // Open the file to read from.
    StreamReader* sr = File::OpenText(path);
    try {
        String* s = S"";
        while (s = sr->ReadLine()) {
            Console::WriteLine(s);
        }
    } __finally {
        if (sr) __try_cast<IDisposable*>(sr)->Dispose();
    }
}

[JScript] No example is available for JScript. To view a Visual Basic, C#, or C++ example, click the Language Filter button Language Filter in the upper-left corner of the page.

Requirements

Platforms: Windows 98, Windows NT 4.0, Windows Millennium Edition, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003 family, .NET Compact Framework, Common Language Infrastructure (CLI) Standard

.NET Framework Security: 

See Also

File Class | File Members | System.IO Namespace | StreamWriter | Working with I/O | Reading Text from a File | Writing Text to a File | Basic File I/O | Reading and Writing to a Newly Created Data File

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