使用 TPL 实现经典异步模式

发布于 2024-10-19 19:54:55 字数 781 浏览 8 评论 0原文

我正在尝试为 WF 4 实现自定义 TrackingParticipant。我可以编写 Track 方法，但我的实现会很慢。

如何使用 .NET 4.0 的任务并行库 (TPL) 实现 Begin/EndTrack 覆盖？我看过 TPL 和传统 .NET 异步编程，但我没有确定如何在这里应用它。

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
    }
}

原文

I'm trying to implement a custom TrackingParticipant for WF 4. I can write the Track method, but my implementation will be slow.

How can I implement the Begin/EndTrack overrides using .NET 4.0's Task Parallel Library (TPL)? I've looked at TPL and Traditional .NET Asynchronous Programming but am not sure how to apply it here.

Note that TrackingParticipant is part of .NET and has the Classic Async Pattern predefined using virtual methods.

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
    }
}

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寒冷纷飞旳雪 2024-10-26 19:54:55

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 Task 的 Result 属性，而不是仅仅调用等等。例如：

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;
}

This is the generic pattern with which to implement the classic APM programming model:

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();
}

If the EndXXX method returned a result you would actually return the Result property of the Task instead of just calling Wait. For example:

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;
}

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