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
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:
- FileIOPermission for appending to the specified file. Associated enumeration: FileIOPermissionAccess.Append
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