FileSystemWatcher calls handler three times

Question

I have written a test app to try out the FileSystemWatcher example code from msdn.

It basically works but the handler gets called three times. Does any one know why?

namespace FileWatcherTest
{
    public partial class Form1 : Form
    {
        private FileSystemWatcher watcher;
        public Form1()
        {
            InitializeComponent();
            string testPath = 
                Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments) 
                + @"\Test";
            InitialiseFileWatcher(testPath, "example.txt");
        }

        private void InitialiseFileWatcher(string path, string fileName)
        {
            watcher = new FileSystemWatcher();
            watcher.Path = path;
            watcher.NotifyFilter = NotifyFilters.LastWrite;
            watcher.Filter = fileName;
            watcher.Changed += new FileSystemEventHandler(OnFarmListChanged);
            // Begin watching.
            watcher.EnableRaisingEvents = true;
        }

        private static void OnFarmListChanged(object source, FileSystemEventArgs e)
        {
            string text = "File: " + e.FullPath + " " + e.ChangeType;
            MessageBox.Show(text);
        }
    }
}

score 1 · Accepted Answer · answered Oct 14 '13 at 20:36

As part of the documentation in the link you included:

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.

FileSystemWatcher calls handler three times

1 Answers1