Changed Event
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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)

public event FileSystemEventHandler Changed

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.


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.


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 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.

using System;
using System.IO;
using System.Security.Permissions;

public class Watcher

    public static void Main()


    [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)");

        // 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.");

    // 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);

.NET Framework
Available since 1.1
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