using System;
using System.IO;

namespace ConsoleApplication1
{
 public class LogReader
 {
  private readonly FileSystemWatcher _watcher;
  private readonly StreamReader      _reader;
  //---------------------------------------------------------------------
  public LogReader(string logFileFullName)
  {
   _watcher              = new FileSystemWatcher();
   _watcher.Path         = Path.GetDirectoryName(logFileFullName);
   _watcher.Filter       = Path.GetFileName(logFileFullName);
   _watcher.NotifyFilter = NotifyFilters.LastWrite;
   _watcher.Changed     += watcher_Changed;

   FileStream fs = new FileStream(
    logFileFullName, 
    FileMode.Open, 
    FileAccess.Read, 
    FileShare.ReadWrite);

   _reader       = new StreamReader(fs);
  }
  //---------------------------------------------------------------------
  void watcher_Changed(object sender, FileSystemEventArgs e)
  {
   this.LogEntryAdded(_reader.ReadLine());
  }
  //---------------------------------------------------------------------
  public void Start()
  {
   _watcher.EnableRaisingEvents = true;
  }
  //---------------------------------------------------------------------
  public void Stop()
  {
   _watcher.EnableRaisingEvents = false;
  }
  //---------------------------------------------------------------------
  public event Action<string> LogEntryAdded = delegate { };
 }
}