在项目中需要用FileSystemWatcher对单个文件内容进行监视，文件中每添加一行则需要Fire相应的事件，代码如下
public class CommandWatcher
{
public event EventHandler<CommandEventArgs> CommandHandler; 
Fields Fields public CommandWatcher(string cmdfile)
{ this.fileName = cmdfile; isChangeImmediate = true; 
} // // Summary: // Raises the System.IO.FileSystemWatcher.Changed event. // // Parameters: // e: // A System.IO.FileSystemEventArgs that contains the event data. protected void OnChanged(object sender, FileSystemEventArgs e) { ReloadFile(); } // // Summary: // Raises the System.IO.FileSystemWatcher.Error event. // // Parameters: // e: // An System.IO.ErrorEventArgs that contains the event data. protected void OnError(object sender, ErrorEventArgs e) { } // // Summary: // Raises the System.IO.FileSystemWatcher.Renamed event. // // Parameters: // e: // A System.IO.RenamedEventArgs that contains the event data. protected void OnRenamed(object sender, RenamedEventArgs e) { } /// <summary> /// Hook up for the currently selected monitoring method. /// </summary> public void Start() { if (isChangeImmediate) { // stop timer if running ClearTimer(); // If a file is set and the watcher has not been set up yet then create it if (null != fileName && null == watcher) { string path = Path.GetDirectoryName(fileName); string baseName = Path.GetFileName(fileName); // Use the FileSystemWatcher class to detect changes to the log file immediately // We must watch for Changed, Created, Deleted, and Renamed events to cover all cases watcher = new System.IO.FileSystemWatcher(path, baseName); FileSystemEventHandler handler = new FileSystemEventHandler(OnChanged); watcher.Changed += handler; watcher.Created += handler; watcher.Deleted += handler; watcher.Renamed += OnRenamed; // Without setting EnableRaisingEvents nothing happens watcher.EnableRaisingEvents = true; } } else { // On a timer so clear the watcher if previously set up ClearWatcher(); int numSeconds = 5; if (null != timer) { // Timer is already running so just make sure the interval is correct if (timer.Interval != 1000 * numSeconds) { timer.Interval = 1000 * numSeconds; } } else { // Fire up a timer if the user entered a valid time interval if (0 != numSeconds) { timer = new System.Windows.Forms.Timer(); timer.Interval = 1000 * numSeconds; timer.Tick += timerTick; timer.Start(); } } } this.ReloadFile(); } void timerTick(object sender, EventArgs e) { UpdateBasedOnFileTime(); } /// <summary> /// Update the log file if the modified timestamp has changed since the last time the file was read. /// </summary> private void UpdateBasedOnFileTime() { if (null != fileName) { // This returns "12:00 midnight, January 1, 1601 A.D." if the file does not exist DateTime newLastModifiedTime = File.GetLastWriteTime(fileName); if ((newLastModifiedTime.Year < 1620 && newLastModifiedTime != lastModifiedTime) || newLastModifiedTime > lastModifiedTime) { //OnLogFileChanged(); ReloadFile(); } } } /// <summary> /// Read the log file. /// </summary> /// <remarks>If the user has some text selected then keep that text selected.</remarks> private void ReloadFile() { if (reloadingFile) return; // already busy doing this reloadingFile = true; try { if (null == fileName) { // textBoxContents.Text = ""; } else { string newFileLines = ""; lastModifiedTime = File.GetLastWriteTime(fileName); // Remember when we last read in this file long newLength = 0; // will be set properly later if all is well bool fileExists = File.Exists(fileName); bool needToClear = !fileExists; if (fileExists) { // It is possible the file will be in use when we read it (especially if using Immediate mode) // So, we will try up to 5 times to access the file int count = 0; bool success = false; while (count < 5 && !success) { try { // Open with the least amount of locking possible using (FileStream stream = File.Open(fileName, FileMode.Open, FileAccess.ReadWrite, FileShare.ReadWrite)) { newLength = stream.Length; if (newLength >= lastFileSize) { stream.Position = lastFileSize; // Only read in new lines added } else { needToClear = true; } using (StreamReader reader = new StreamReader(stream)) { newFileLines = reader.ReadToEnd(); if (newFileLines != string.Empty) { if (this.CommandHandler != null) this.CommandHandler(this, new CommandEventArgs(newFileLines)); } //string []tmp = newFileLines.Split(seprater, StringSplitOptions.RemoveEmptyEntries); } } success = true; } catch (IOException) { System.Threading.Thread.Sleep(50); // Give a little while to free up file } ++count; } } // Remember the current file length so we can read only newly added log lines the next time the log file is read lastFileSize = newLength; if(lastFileSize > 1024 * 1024 * 2) { File.Delete(fileName); File.Create(fileName); } if (0 != newFileLines.Length) { // See if this log file has proper cr/lf and if not convert int lastCr = newFileLines.LastIndexOf('\n'); if (-1 != lastCr && 0 < lastCr) { if (newFileLines[lastCr - 1] != '\r') { // OK, this file only has Cr and we need to convert to CrLf newFileLines = newFileLines.Replace("\n", "\r\n"); } } } } } finally { // Put clearing this flag in a finally so we know it will be cleared reloadingFile = false; } } /// <summary> /// Cleanup the <see cref="Timer"/> /// </summary> private void ClearTimer() { if (null != timer) { timer.Tick -= timerTick; timer.Dispose(); timer = null; } } /// <summary> /// Cleanup the <see cref="FileSystemWatcher"/> /// </summary> private void ClearWatcher() { if (null != watcher) { FileSystemEventHandler handler = new FileSystemEventHandler(OnChanged); watcher.Changed -= handler; watcher.Created -= handler; watcher.Deleted -= handler; watcher.Renamed -= OnRenamed; watcher.Dispose(); watcher = null; } }
}