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5.3. Copy, Move, and Delete Files
In
addition
to helping you gather information about the directories and files on
your system, the My.Computer.FileSystem object
also gives you quick access to a number of methods for performing
common file-management tasks, such as copying, moving, and deleting
files.
Note: In VB 2005, you can perform common file-management tasks
with a single line of code.
5.3.1. How do I do that?
The My.Computer.FileSystem object provides several
self-contained methods for performing common file-management
operations. They are:
CopyFile( )
and CopyDirectory( )
MoveFile( )
and MoveDirectory( )
RenameFile( )
and RenameDirectory()
DeleteFile( )
and DeleteDirectory()
The way you use each of these methods is fairly straightforward. You
supply two parameters: a source path and, if required, a target
filename or path. For example, you can rename a file with this line
of code:
My.Computer.FileSystem.RenameFile("c:\myfile.txt", "newname.txt")These methods are also available in overloaded versions that give you
additional features. We'll take a look at those
next.
The move and copy methods of FileSystem are
available in a variety of overloaded versions. If you need to
overwrite an existing file or directory, be sure to use a version
that includes the Boolean parameter overwrite and
set it to true. Otherwise, you'll
receive an exception and the operation won't be
completed. Here's an example of one such option:
Note: In some beta versions, the user interface for moving or
deleting a file doesn't appear, even when you choose
to see it. However, the underlying task (moving or deleting a file)
is always performed correctly.
My.Computer.FileSystem.CopyDirectory("c:\MyFiles", _
"c:\CopyOfMyFiles", True)Interestingly, among the copying and deleting methods are versions
that accept the showUI Boolean parameter. If that
parameter is set to TRue, the operation works
exactly as if a user had initiated the delete or copy operation in
Windows Explorer: dialog boxes appear asking the user to confirm the
request to overwrite or delete files, and a progress indicator
appears with a Cancel button when a file copy or delete operation is
in progress (unless the operation completes very quickly). You can
even specify what should happen when the user clicks Cancel (either
an exception is thrown or nothing at all happens) using the
onUserCancel parameter.
Example 5-3 provides a complete console application
that lets you test this behavior.
Example 5-3. Moving and deleting files with Windows UI
Imports System.IO
Module FileManagement
Public Sub Main( )
' Create a large test file (100 MB).
Dim TestFile As String = "c:\test.bin"
Console.WriteLine("Creating file...")
Dim fs As FileStream = File.OpenWrite(TestFile)
For i As Integer = 1 To 100000000
fs.WriteByte(0)
Next
fs.Close( )
' Create the target directory.
Console.WriteLine("Creating directory...")
Dim TargetDir As String = "c:\TestDir"
My.Computer.FileSystem.CreateDirectory(TargetDir)
Dim TargetFile As String = Path.Combine(TargetDir, "test.bin")
Console.WriteLine("Moving file...")
' Try moving the file. Set the following parameters:
' showUI = UIOption.AllDialogs
' (Show all the Windows UI, not just error messages.)
' onUserCancel = UICancelOption.ThrowException
' (Generate an error if the user clicks Cancel.)
Try
My.Computer.FileSystem.MoveFile(TestFile, TargetFile, _
UIOption.AllDialogs, UICancelOption.ThrowException)
Console.WriteLine("File moved.")
Catch Err As Exception
Console.WriteLine("You canceled the operation.")
' Remove the original file.
My.Computer.FileSystem.DeleteFile(TestFile)
End Try
Console.WriteLine("Press Enter to continue.")
Console.ReadLine( )
' Delete the target directory. Set the following parameters:
' showUI = UIOption.AllDialogs
' (Show the confirmation and Windows UI dialog box.)
' sendToRecycleBin = RecycleOption.SendToRecycleBin
' (Delete the file permanently.
' onUserCancel = UICancelOption.DoNothing
' (Allow the user to cancel this operation.)
My.Computer.FileSystem.DeleteDirectory(TargetDir, _
UIOption.AllDialogs, RecycleOption.SendToRecycleBin, _
UICancelOption.DoNothing)
Console.WriteLine("Cleanup finished.")
End Sub
End Module
As shown in this example, the DeleteFile( ) and
DeleteDirectory( ) methods have one additional
frill available. By default, when you delete a file, it bypasses the
Windows recycle bin. However, you can use an
overloaded version of DeleteFile( ) or
DeleteDirectory( ) that accepts a
sendToRecycleBin parameter. Set this to
true to keep your file around as a safeguard.
5.3.2. What about...
...file operations that use special
folders? The new My.Computer.FileSystem object
allows you to retrieve references to many system-defined folders
through the SpecialDirectories class.
For example, you can quickly retrieve the
path for temporary files, user documents, and the desktop.
Here's an example:
Dim Desktop As String = My.Computer.FileSystem.SpecialDirectories.Desktop
Console.WriteLine("Your desktop is at: " & Desktop)
Console.Write("It's size is: ")
Console.Write(My.Computer.FileSystem.GetDirectoryInfo(Desktop).Size)
Console.WriteLine(" bytes")
Console.Write("It contains: ")
Console.Write(My.Computer.FileSystem.GetFiles(Desktop).Count)
Console.WriteLine(" files")
The SpecialDirectories class includes all the
following properties, each of which returns a string with the
corresponding fully qualified path:
AllUsersApplicationDataCurrentUserApplicationDataDesktopMyDocumentsMyMusic MyPicturesProgramsTemp
