Question

Im利用Reactive Expansions Library on .Net 3.5的任务部分。

它的工作大多顺利进行,但是在一个地方,它两次提出同样的任务。

这一呼吁是:

Task.Factory.StartNew(
    () => Processor.ProcessMessage(incomingMessage),
    TaskCreationOptions.PreferFairness );

任何想法? 这难道是一种ug吗?

页: 1

i think the problem is with the way c# does closure in lambdas. the problem wasn"t in the TPL, the same problem returned with the plain old thread pool.

并解决了这一问题:

foreach (var Processor in processors)
{
 object[] crap = new object[2];
 crap[0] = Processor;
 crap[1] = incomingMessage;
 Task.Factory.StartNew(Magic, crap, TaskCreationOptions.PreferFairness);
}

public void Magic(object obj)
{
 object[] crap =(object[]) obj;
 ((IIncomingMessageProcessor)crap[0]).ProcessMessage((IncomingMessageBase)crap[1]);
}

原始来源是:

foreach (var Processor in processors)
{
Task.Factory.StartNew(
    () => Processor.ProcessMessage(incomingMessage),
    TaskCreationOptions.PreferFairness );
}

这样一来,在加工商周围就关闭了,而我猜测问题在于,它正在把同样的物体回收到lam中,并对加工商进行冲撞。

页: 1 2

I m convinced this is the problem. i refactored and debugged the System.Threading.dll both times i create the task, it is created with the same delegate(Same ObjectID) and the Processor changes in the Target property between iterations. anyone knows a good work around?

页: 1 3 this works too(thanks Judah Himango):

foreach (var processor in processors)
{
 var crap = processor;
 Task.Factory.StartNew(() => crap.ProcessMessage(incomingMessage), TaskCreationOptions.PreferFairness);
}

Answer 1

你们是否在lam子里使用 lo素变量? e.g.

foreach (var foo in blah)
{
   // You re capturing foo inside a lambda -- this probably won t do what you think it will!
   Task.Factory.StartNew(() => foo.Something()); 
}

见。为什么不使用斜线表示的变异?

www.un.org/Depts/DGACM/index_french.htm 2012年11月: 新的C第5号汇编者通过改变行为来应对这一混淆领域,从而捕获了每种 lo状变量,即预期行为。 Eric Lippert of the C# Team writes ,

We are taking the breaking change. In C# 5, the loop variable of a foreach will be logically inside the loop, and therefore closures will close over a fresh copy of the variable each time. The "for" loop will not be changed.

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