使用TPL实现经典异步模式

Question

我正在尝试为WF 4实现自定义TrackingParticipant.我可以编写Track方法,但我的实现速度很慢.

如何使用.NET 4.0的任务并行库(TPL)实现Begin/EndTrack覆盖？我看过TPL和Traditional .NET异步编程,但我不知道如何在这里应用它.

请注意,TrackingParticipant是.NET的一部分,并具有使用虚拟方法预定义的经典异步模式.

public class MyTrackingParticipant : TrackingParticipant
{
    protected override IAsyncResult BeginTrack(
        TrackingRecord record, TimeSpan timeout,
        AsyncCallback callback, object state)
    {
        // ?
    }

    protected override void EndTrack(IAsyncResult result)
    {
        // ?
    }

    protected override void Track(TrackingRecord record, TimeSpan timeout)
    {
        // synchronous code to be called
    }
}

Answer 1

这是实现经典APM编程模型的通用模式:

protected override IAsyncResult BeginTrack(TrackingRecord record, TimeSpan timeout, AsyncCallback callback, object state)
{
    Task result = Task.Factory.StartNew(
        (taskState) =>
        {
           // ... your async work here ...
        },
        state);

    if(callback != null)
    {
        result.ContinueWith((t) => callback(t));
    }

    return result;
}

protected override void EndTrack(IAsyncResult asyncResult)
{
   // Call wait to block until task is complete and/or cause any exceptions that occurred to propagate to the caller
   ((Task)asyncResult).Wait();
}

如果EndXXX方法返回结果,您实际上将返回而不是仅调用的Result属性.例如:TaskWait

protected override int EndAwesomeCalculation(IAsyncResult asyncResult)
{
   // This will block until the result is available and/or cause any exceptions that occurred propagate to the caller
   return ((Task<int>)asyncResult).Result;
}