使用异步委托或 ThreadPool.QueueUserWorkItem 实现大规模并行性？

问：

我有一个 .NET 应用程序，在批量导入中处理大约 300,000 条记录，每条记录需要几秒钟，因此我想并行化它。在下面的代码中，和有什么不一样？ProcessWithAnsycDelegates()ProcessWithThreadPool()

public class ResultNotification
 { public EventHandler event Success;
   public EventHandler event Fail;
   internal void Notify(bool sucess) {if (success) Success(); else Fail();}
 }

public static class Processor
 { public ResultNotification ProcessWithAnsycDelegates(Record record)
    { var r = new ResultNotification();
      Func<Record,bool> processRecord=new RecordProcessor().ProcessRecord;
      processRecord.BeginInvoke
                     ( record
                      ,ar => result.Notify(processRecord.EndInvoke(ar))
                      ,null); 
      return r;    
    }

   public ResultNotification ProcessWithThreadPool(Record r)
    { var r  = new ResultNotification();
      var rp = new RecordProcessor();
      ThreadPool.QueueWorkUserItem(_=>result.Notify(rp.ProcessRecord(r)));
      return r;
    }
 }