Occurs when a file or directory in the specified Path is changed.
Namespace:
System.IO
Assembly:
System (in System.dll)
Visual Basic (Declaration)
<IODescriptionAttribute("FSW_Changed")> _
Public Event Changed As FileSystemEventHandler
Dim instance As FileSystemWatcher
Dim handler As FileSystemEventHandler
AddHandler instance.Changed, handler
[IODescriptionAttribute("FSW_Changed")]
public event FileSystemEventHandler Changed
[IODescriptionAttribute(L"FSW_Changed")]
public:
event FileSystemEventHandler^ Changed {
void add (FileSystemEventHandler^ value);
void remove (FileSystemEventHandler^ value);
}
JScript does not support events.
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. |
The following example uses the Changed event to display the file path to the console whenever the watched file is changed.
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
public class Watcher
{
public static void Main()
{
Run();
}
[PermissionSet(SecurityAction.Demand, Name="FullTrust")]
public static void Run()
{
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;
}
// Create a new FileSystemWatcher and set its properties.
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 += new FileSystemEventHandler(OnChanged);
watcher.Created += new FileSystemEventHandler(OnChanged);
watcher.Deleted += new FileSystemEventHandler(OnChanged);
watcher.Renamed += new RenamedEventHandler(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: {0} renamed to {1}", e.OldFullPath, e.FullPath);
}
}
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' )
;
}
};
int main() {
Watcher::run();
}
Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98
The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.
.NET Framework
Supported in: 3.5, 3.0, 2.0, 1.1, 1.0
Reference