FileSystemWatcher.Changed Event
Definition
Occurs when a file or directory in the specified Path is changed.
public:
event System::IO::FileSystemEventHandler ^ Changed;
public event System.IO.FileSystemEventHandler? Changed;
public event System.IO.FileSystemEventHandler Changed;
[System.IO.IODescription("FSW_Changed")]
public event System.IO.FileSystemEventHandler Changed;
[System.IO.IODescription("Occurs when a file/directory change matches the filter")]
public event System.IO.FileSystemEventHandler Changed;
member this.Changed : System.IO.FileSystemEventHandler
[<System.IO.IODescription("FSW_Changed")>]
member this.Changed : System.IO.FileSystemEventHandler
[<System.IO.IODescription("Occurs when a file/directory change matches the filter")>]
member this.Changed : System.IO.FileSystemEventHandler
Public Custom Event Changed As FileSystemEventHandler
Event Type
- Attributes
Examples
The following example uses the Changed event to display the file path to the console whenever the watched file is changed.
#using <System.dll>
using namespace System;
using namespace System::IO;
using namespace System::Security::Permissions;
public ref class Watcher
{
private:
// Define the event handlers.
static void OnChanged( Object^ /*source*/, FileSystemEventArgs^ e )
{
// Specify what is done when a file is changed, created, or deleted.
Console::WriteLine( "File: {0} {1}", e->FullPath, e->ChangeType );
}
static void OnRenamed( Object^ /*source*/, RenamedEventArgs^ e )
{
// Specify what is done when a file is renamed.
Console::WriteLine( "File: {0} renamed to {1}", e->OldFullPath, e->FullPath );
}
public:
[PermissionSet(SecurityAction::Demand, Name="FullTrust")]
int static run()
{
array<String^>^args = System::Environment::GetCommandLineArgs();
// If a directory is not specified, exit program.
if ( args->Length != 2 )
{
// Display the proper way to call the program.
Console::WriteLine( "Usage: Watcher.exe (directory)" );
return 0;
}
// Create a new FileSystemWatcher and set its properties.
FileSystemWatcher^ watcher = gcnew FileSystemWatcher;
watcher->Path = args[ 1 ];
/* Watch for changes in LastAccess and LastWrite times, and
the renaming of files or directories. */
watcher->NotifyFilter = static_cast<NotifyFilters>(NotifyFilters::LastAccess |
NotifyFilters::LastWrite | NotifyFilters::FileName | NotifyFilters::DirectoryName);
// Only watch text files.
watcher->Filter = "*.txt";
// Add event handlers.
watcher->Changed += gcnew FileSystemEventHandler( Watcher::OnChanged );
watcher->Created += gcnew FileSystemEventHandler( Watcher::OnChanged );
watcher->Deleted += gcnew FileSystemEventHandler( Watcher::OnChanged );
watcher->Renamed += gcnew RenamedEventHandler( Watcher::OnRenamed );
// Begin watching.
watcher->EnableRaisingEvents = true;
// Wait for the user to quit the program.
Console::WriteLine( "Press \'q\' to quit the sample." );
while ( Console::Read() != 'q' );
return 0;
}
};
int main() {
Watcher::run();
}
using System;
using System.IO;
using System.Security.Permissions;
public class Watcher
{
public static void Main()
{
Run();
}
[PermissionSet(SecurityAction.Demand, Name = "FullTrust")]
private static void Run()
{
string[] args = Environment.GetCommandLineArgs();
// If a directory is not specified, exit program.
if (args.Length != 2)
{
// Display the proper way to call the program.
Console.WriteLine("Usage: Watcher.exe (directory)");
return;
}
// Create a new FileSystemWatcher and set its properties.
using (FileSystemWatcher watcher = 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
| NotifyFilters.LastWrite
| NotifyFilters.FileName
| NotifyFilters.DirectoryName;
// Only watch text files.
watcher.Filter = "*.txt";
// Add event handlers.
watcher.Changed += OnChanged;
watcher.Created += OnChanged;
watcher.Deleted += OnChanged;
watcher.Renamed += OnRenamed;
// Begin watching.
watcher.EnableRaisingEvents = true;
// Wait for the user to quit the program.
Console.WriteLine("Press 'q' to quit the sample.");
while (Console.Read() != 'q') ;
}
}
// Define the event handlers.
private static void OnChanged(object source, FileSystemEventArgs e) =>
// Specify what is done when a file is changed, created, or deleted.
Console.WriteLine($"File: {e.FullPath} {e.ChangeType}");
private static void OnRenamed(object source, RenamedEventArgs e) =>
// Specify what is done when a file is renamed.
Console.WriteLine($"File: {e.OldFullPath} renamed to {e.FullPath}");
}
Imports System.IO
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 = 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.
Using 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 Using
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: {e.OldFullPath} renamed to {e.FullPath}")
End Sub
End Class
Remarks
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.
Note
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.
Note
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.
Note
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
.