关于System.Diagnostics.Trace类的问题

Question

/// /// The main entry point for the application. /// [STAThread]  public static void Main() {  try { // setup generic exception handler... SWF.Application.ThreadException += new ST.ThreadExceptionEventHandler(App.OnAppException); // setup cleanup routine for normal app shutdown... SWF.Application.ThreadExit += new System.EventHandler(App.OnAppExit); // when app starts, delete the previous log file (if any) string logfile = System.AppDomain.CurrentDomain.BaseDirectory + "AppLog.txt"; System.IO.TextWriter log = new System.IO.StreamWriter(logfile);  if (Globals.Trace) // then also send trace output to log file? { System.Diagnostics.TextWriterTraceListener logger; logger = new System.Diagnostics.TextWriterTraceListener(log); System.Diagnostics.Trace.Listeners.Add(logger); System.Diagnostics.Trace.Write("App starting: " + DateTime.Now); } SWF.Application.Run(new Form1()); } catch(Exception ex) { OnAppException(null, new ST.ThreadExceptionEventArgs(ex)); }   以上是利用Trace类来记录程序运行日志的代码，可每次当应用程序重启后，AppLog.txt文件里以前的内容就被覆盖了。谁知道这个问题怎么解决呢？