Question

If I’m reading a text file in shared access mode and another process truncates it, what is the easiest way to detect that? (I’m excluding the obvious choice of refreshing a FileInfo object periodically to check its size) Is there some convenient way to capture an event? (Filewatcher?)

Answer 1

There is, It’s called FileSystemWatcher.

If you are developing a windows forms application, you can drag-and-drop it from the toolbox.

Here’s some usage example:

private void myForm_Load(object sender, EventArgs e) {     var fileWatcher = new System.IO.FileSystemWatcher();      // Monitor changes to PNG files in C:\temp and subdirectories     fileWatcher.Path = @'C:\temp';     fileWatcher.IncludeSubdirectories = true;     fileWatcher.Filter = @'*.png';      // Attach event handlers to handle each file system events     fileWatcher.Changed += fileChanged;     fileWatcher.Created += fileCreated;     fileWatcher.Renamed += fileRenamed;      // Start monitoring!     fileWatcher.EnableRaisingEvents = true; }  void fileRenamed(object sender, System.IO.FileSystemEventArgs e) {     // a file has been renamed! }  void fileCreated(object sender, System.IO.FileSystemEventArgs e) {     // a file has been created! }  void fileChanged(object sender, System.IO.FileSystemEventArgs e) {     // a file is modified! } 

It’s in System.IO and System.dll so you should be able to use it in most type of projects.