C# FileSystemWatcher

using System.IO;

//file system watcher object.
        private FileSystemWatcher watcher;
        private delegate void UpdateWatchTextDelegate(string newText);

        public void UpdateWatchText(string newText)
        {
            lblWatch.Text = newText;
        }

        public Form1()
        {
            InitializeComponent();

            this.watcher = new FileSystemWatcher();
            this.watcher.Deleted += new FileSystemEventHandler(watcher_Deleted);
            this.watcher.Renamed += new RenamedEventHandler(watcher_Renamed);
            this.watcher.Changed += new FileSystemEventHandler(watcher_Changed);
            this.watcher.Created += new FileSystemEventHandler(watcher_Created);
        }

        void watcher_Created(object sender, FileSystemEventArgs e)
        {
            //throw new NotImplementedException();
            try
            {
                StreamWriter sw = new StreamWriter("c:\\Log.txt", true);
                sw.WriteLine("File: {0} Created", e.FullPath);
                sw.Close();
                this.BeginInvoke(new UpdateWatchTextDelegate(UpdateWatchText), "Wrote create event to log");
            }
            catch (IOException)
            {
                this.BeginInvoke(new UpdateWatchTextDelegate(UpdateWatchText), "Error Writing to log");
            }
        }

        void watcher_Changed(object sender, FileSystemEventArgs e)
        {
            //throw new NotImplementedException();
            try
            {
                StreamWriter sw = new StreamWriter("c:\\Log.txt", true);
                sw.WriteLine("File: {0} {1}", e.FullPath, e.ChangeType.ToString());
                sw.Close();
                this.BeginInvoke(new UpdateWatchTextDelegate(UpdateWatchText), "Wrote change event to log");
            }
            catch (IOException)
            {
                this.BeginInvoke(new UpdateWatchTextDelegate(UpdateWatchText), "Error Writing to log");
            }
        }

        void watcher_Renamed(object sender, RenamedEventArgs e)
        {
            //throw new NotImplementedException();
            try
            {
                StreamWriter sw = new StreamWriter("c:\\Log.txt", true);
                sw.WriteLine("File renamed from {0} to {1}", e.OldName, e.FullPath);
                sw.Close();
                this.BeginInvoke(new UpdateWatchTextDelegate(UpdateWatchText), "Wrote renamed event to log");
            }
            catch(IOException)
            {
                this.BeginInvoke(new UpdateWatchTextDelegate(UpdateWatchText), "Error Writing to log");
            }
        }

        void watcher_Deleted(object sender, FileSystemEventArgs e)
        {
            //throw new NotImplementedException();
            try
            {
                StreamWriter sw = new StreamWriter("c:\\Log.txt", true);
                sw.WriteLine("File: {0} Deleted", e.FullPath);
                sw.Close();
                this.BeginInvoke(new UpdateWatchTextDelegate(UpdateWatchText), "Wrote delete event to log");
            }
            catch (IOException)
            {
                this.BeginInvoke(new UpdateWatchTextDelegate(UpdateWatchText), "Error Writing to log");
            }
        }

        private void cmdBrowse_Click(object sender, EventArgs e)
        {
            if (FileDialog.ShowDialog() != DialogResult.Cancel)
            {
                txtLocation.Text = FileDialog.FileName;
                cmdWatch.Enabled = true;
            }
        }

        private void cmdWatch_Click(object sender, EventArgs e)
        {
            watcher.Path = Path.GetDirectoryName(txtLocation.Text);//监控路径（文件夹）
            watcher.Filter = "*.*" ;//如果filter为文件名称则表示监控该文件，如果为*.txt则表示要监控指定目录当中的所有.txt文件
            watcher.NotifyFilter = NotifyFilters.LastWrite |
                NotifyFilters.FileName |
                NotifyFilters.Size;
            lblWatch.Text = "Watching " + txtLocation.Text;

            //begin watching.
            watcher.EnableRaisingEvents = true;
        }