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.
using System; using System.IO; using System.Security.Permissions; 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); } }
Available since 1.1
