我正在尝试为WF 4实现一个CustomParticipator.我可以编写Track方法,但是我的实现会很慢.
如何使用.NET 4.0的任务并行库(TPL)实现Begin / EndTrack覆盖？我看过TPL and Traditional .NET Asynchronous Programming,但不知道如何在这里应用.
请注意,TrackingParticipant是.NET的一部分,并使用虚拟方法预定义了“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
}
}
解决方法
这是实现经典APM编程模型的通用模式：
protected override IAsyncResult BeginTrack(TrackingRecord record,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方法返回一个结果,你实际上将返回任务的Result属性,而不是仅仅调用Wait.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;
}
