Assembly: mscorlib (in mscorlib.dll)
The following example appends text to a file and reads from the file.
Imports System Imports System.IO Public Class Test Public Shared Sub Main() Dim fi As FileInfo = New FileInfo("c:\temp\MyTest.txt") Dim sw As StreamWriter ' This text is added only once to the file. If fi.Exists = False Then 'Create a file to write to. sw = fi.CreateText() sw.WriteLine("Hello") sw.WriteLine("And") sw.WriteLine("Welcome") sw.Flush() sw.Close() End If ' This text will always be added, making the file longer over time ' if it is not deleted. sw = fi.AppendText() sw.WriteLine("This") sw.WriteLine("is Extra") sw.WriteLine("Text") sw.Flush() sw.Close() 'Open the file to read from. Dim sr As StreamReader = fi.OpenText() Dim s As String Do While sr.Peek() >= 0 s = sr.ReadLine() Console.WriteLine(s) Loop sr.Close() End Sub End Class 'This code produces output similar to the following; 'results may vary based on the computer/file structure/etc.: ' 'Hello 'And 'Welcome 'This 'is Extra 'Text 'When you run this application a second time, you will see the following output: ' 'Hello 'And 'Welcome 'This 'is Extra 'Text 'This 'is Extra 'Text
The following example demonstrates appending text to the end of a file and also displays the result of the append operation to the console. The first time this routine is called, the file is created if it does not exist. After that, the specified text is appended to the file.
Imports System Imports System.IO Public Class AppendTextTest Public Shared Sub Main() Dim fi As New FileInfo("temp.txt") Dim sw As StreamWriter = fi.AppendText() sw.WriteLine("Add as many lines as you like...") sw.WriteLine("Add another line to the output...") sw.Flush() sw.Close() Dim sr As New StreamReader(fi.OpenRead()) ' Get the information out of the file and display it. ' Remember that the file might have other lines if it already existed. While sr.Peek() <> -1 Console.WriteLine(sr.ReadLine()) End While End Sub 'Main End Class 'AppendTextTest 'This code produces output similar to the following; 'results may vary based on the computer/file structure/etc.: 'Add as many lines as you like... 'Add another line to the output...
Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.