FileSystemWatcher.Changed Event

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

FileSystemEventHandler

Attributes

IODescriptionAttribute

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.

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

Applies to

See also

• NotifyFilter
• OnChanged(FileSystemEventArgs)
• SynchronizingObject
• FileSystemEventArgs
• FileSystemEventHandler