记录错误的最后提示

 if (log.Length > 0)
 {
     var logPath = Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "log.txt");
     System.IO.File.WriteAllText(logPath, log.ToString());
     MessageBox.Show($"完成，发现{log.ToString().Count(c => c == '\n')}个错误，已记录到日志。");
     Process.Start("notepad.exe", logPath);
 }
 else
 {
     MessageBox.Show("完成，未发现错误。");
 }