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FileSystemWatcher.Changed Event

Occurs when a file or directory in the specified Path is changed.

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

'Declaration
<IODescriptionAttribute("FSW_Changed")> _
Public Event Changed As FileSystemEventHandler

The Changed event is raised when changes are made to the size, system attributes, last write time, last access time, or security permissions of a file or directory in the directory being monitored.

NoteNote

Common file system operations might raise more than one event. For example, when a file is moved from one directory to another, several OnChanged and some OnCreated and OnDeleted events might be raised. Moving a file is a complex operation that consists of multiple simple operations, therefore raising multiple events. Likewise, some applications (for example, antivirus software) might cause additional file system events that are detected by FileSystemWatcher.

Use NotifyFilter to restrict the number of notifications raised when this event is handled.

NoteNote

The Changed event is raised unexpectedly when a file is renamed, but is not raised when a directory is renamed. To watch for renaming, use the Renamed event.

NoteNote

The order in which the Changed event is raised in relation to the other FileSystemWatcher events may change when the SynchronizingObject property is not Nothing.

The following example uses the Changed event to display the file path to the console whenever the watched file is changed.

Imports System
Imports System.IO
Imports Microsoft.VisualBasic
Imports System.Security.Permissions

Public Class Watcher

    Public Shared Sub Main()
	
         Run()

    End Sub

    <PermissionSet(SecurityAction.Demand, Name:="FullTrust")> _
    Private Shared Sub Run

      Dim args() As String = System.Environment.GetCommandLineArgs()
        ' If a directory is not specified, exit the program. 
        If args.Length <> 2 Then 
            ' Display the proper way to call the program.
            Console.WriteLine("Usage: Watcher.exe (directory)")
            Return 
        End If 

        ' Create a new FileSystemWatcher and set its properties. 
        Dim watcher As New FileSystemWatcher()
        watcher.Path = args(1)
        ' Watch for changes in LastAccess and LastWrite times, and 
        ' the renaming of files or directories. 
        watcher.NotifyFilter = (NotifyFilters.LastAccess Or NotifyFilters.LastWrite Or NotifyFilters.FileName Or NotifyFilters.DirectoryName)
        ' Only watch text files.
        watcher.Filter = "*.txt" 

        ' Add event handlers. 
        AddHandler watcher.Changed, AddressOf OnChanged
        AddHandler watcher.Created, AddressOf OnChanged
        AddHandler watcher.Deleted, AddressOf OnChanged
        AddHandler watcher.Renamed, AddressOf OnRenamed

        ' Begin watching.
        watcher.EnableRaisingEvents = True 

        ' Wait for the user to quit the program.
        Console.WriteLine("Press 'q' to quit the sample.")
        While Chr(Console.Read()) <> "q"c
        End While 
    End Sub 

    ' Define the event handlers. 
    Private Shared Sub OnChanged(source As Object, e As FileSystemEventArgs)
        ' Specify what is done when a file is changed, created, or deleted.
        Console.WriteLine("File: " & e.FullPath & " " & e.ChangeType)
    End Sub     

    Private Shared Sub OnRenamed(source As Object, e As RenamedEventArgs)
        ' Specify what is done when a file is renamed.
        Console.WriteLine("File: {0} renamed to {1}", e.OldFullPath, e.FullPath)
    End Sub 

End Class

.NET Framework

Supported in: 4.5.2, 4.5.1, 4.5, 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

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