事件的定义

//定义事件，关键字'event',类型EventHandler
public event EventHandler LogPrintCompleted
{
   add
   {
          _logPrintCompleted -= value;//先减后加，避免重复订阅
          _logPrintCompleted += value;
    }
    remove
   {
          _logPrintCompleted -= value;
    }
}  
public event EventHandler _logPrintCompleted = null;

//触发事件的方法
private void onRaiseSanpCompleted(object sender,LogPrintEventArgs e)
{
 if(_logPrintCompleted != null)
 {
     Delegate[] delegates = _logPrintCompleted.GetInvocationList();
     if(delegates != null)
         foreach(EventHandler spi in delegates)
         {
             spi.BeginInvoke(this,e,null,null);
         }
 }    
}