FileSystemEventHandler-Delegat

Artikel
08/20/2007

Stellt die Methode dar, die das Changed-Ereignis, das Created-Ereignis oder das Deleted-Ereignis einer FileSystemWatcher-Klasse behandelt.

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

Syntax

'Declaration
Public Delegate Sub FileSystemEventHandler ( _
    sender As Object, _
    e As FileSystemEventArgs _
)
'Usage
Dim instance As New FileSystemEventHandler(AddressOf HandlerMethod)

public delegate void FileSystemEventHandler (
    Object sender,
    FileSystemEventArgs e
)

public delegate void FileSystemEventHandler (
    Object^ sender, 
    FileSystemEventArgs^ e
)

/** @delegate */
public delegate void FileSystemEventHandler (
    Object sender, 
    FileSystemEventArgs e
)

JScript unterstützt die Verwendung von Delegaten, aber nicht die Deklaration von neuen Delegaten.

Parameter

sender
Die Quelle des Ereignisses.

e
Das FileSystemEventArgs, das die Ereignisdaten enthält.

Hinweise

Beim Erstellen eines FileSystemEventHandler-Delegaten bestimmen Sie die Methode für die Ereignisbehandlung. Um das Ereignis dem Ereignishandler zuzuordnen, fügen Sie dem Ereignis eine Instanz des Delegaten hinzu. Der Ereignishandler wird bei jedem Eintreten des Ereignisses aufgerufen, sofern der Delegat nicht entfernt wird. Weitere Informationen über Ereignishandlerdelegaten finden Sie unter Ereignisse und Delegaten.

Beispiel

Im folgenden Beispiel wird die Erstellung einer FileSystemWatcher-Komponente veranschaulicht, mit der Dateiänderungen (Erstellen, Löschen, Umbenennen, Änderungen) auf einem Laufwerk überwacht werden sollen. Im Beispiel wird auch veranschaulicht, wie Fehlerbenachrichtigungen ordnungsgemäß empfangen werden.

Imports System.IO

Module Module1
    Sub Main()
        ' Create a FileSystemWatcher to monitor all files on drive C.
        Dim fsw As New FileSystemWatcher("C:\")

        ' Watch for changes in LastAccess and LastWrite times, and
        ' the renaming of files or directories. 
        fsw.NotifyFilter = (NotifyFilters.LastAccess Or NotifyFilters.LastWrite _ 
            Or NotifyFilters.FileName Or NotifyFilters.DirectoryName)

        ' Register a handler that gets called when a 
        ' file is created, changed, or deleted.
        AddHandler fsw.Changed, New FileSystemEventHandler(AddressOf OnChanged)

        ' The commented line of code below is a shorthand of the above line.
        ' AddHandler fsw.Changed, AddressOf OnChanged

        ' NOTE: The shorthand version is used in the remainder of this code.
        ' FileSystemEventHandler
        AddHandler fsw.Created, AddressOf OnChanged 
        ' FileSystemEventHandler
        AddHandler fsw.Deleted, AddressOf OnChanged

        ' Register a handler that gets called when a file is renamed.
        ' RenamedEventHandler
        AddHandler fsw.Renamed, AddressOf OnRenamed

        ' Register a handler that gets called if the 
        ' FileSystemWatcher needs to report an error.
        ' ErrorEventHandler
        AddHandler fsw.Error, AddressOf OnError

        ' Begin watching.
        fsw.EnableRaisingEvents = True

        ' Wait for the user to quit the program.
        Console.WriteLine("Press 'Enter' to quit the sample.")
        Console.ReadLine()
    End Sub

    ' This method is called when a file is created, changed, or deleted.
    Private Sub OnChanged(ByVal source As Object, ByVal e As FileSystemEventArgs)

        ' Show that a file has been created, changed, or deleted.
        Dim wct As WatcherChangeTypes = e.ChangeType
        Console.WriteLine("File {0} {1}", e.FullPath, wct.ToString())
    End Sub

    ' This method is called when a file is renamed.
    Private Sub OnRenamed(ByVal source As Object, ByVal e As RenamedEventArgs)

        ' Show that a file has been renamed.
        Dim wct As WatcherChangeTypes = e.ChangeType
        Console.WriteLine("File {0} {2} to {1}", e.OldFullPath, e.FullPath, wct.ToString())
    End Sub

    ' This method is called when the FileSystemWatcher detects an error.
    Private Sub OnError(ByVal source As Object, ByVal e As ErrorEventArgs)

        ' Show that an error has been detected.
        Console.WriteLine("The FileSystemWatcher has detected an error")

        ' Give more information if the error is due to an internal buffer overflow.
        If TypeOf e.GetException Is InternalBufferOverflowException Then
            ' This can happen if Windows is reporting many file system events quickly 
            ' and internal buffer of the  FileSystemWatcher is not large enough to handle this
            ' rate of events. The InternalBufferOverflowException error informs the application
            ' that some of the file system events are being lost.
            Console.WriteLine( _
                "The file system watcher experienced an internal buffer overflow: " _
                + e.GetException.Message)
        End If
    End Sub
End Module

Plattformen

Windows 98, Windows 2000 SP4, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

.NET Framework unterstützt nicht alle Versionen sämtlicher Plattformen. Eine Liste der unterstützten Versionen finden Sie unter Systemanforderungen.

Versionsinformationen

.NET Framework

Unterstützt in: 2.0, 1.1, 1.0

Siehe auch

Referenz

System.IO-Namespace
Changed
Created
Deleted
FileSystemEventArgs-Klasse
FileSystemWatcher
InternalBufferOverflowException
NotifyFilters
RenamedEventArgs
RenamedEventHandler
WaitForChangedResult
WatcherChangeTypes

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