FileSystemWatcher.Changed Event
Occurs when a file or directory in the specified Path is changed.
Assembly: System (in System.dll)
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.
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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.
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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. |
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The order in which the Changed event is raised in relation to the other FileSystemWatcher events may change when the SynchronizingObject property is not null. |
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
Available since 1.1
