多线程：Waiteall不等待预期

Question

我有一个呼叫两个单独的线程来做一些线程。每当任何作业都完成了WATHANDLE.SET（0被调用，并且在父工人线程的末尾，我想在继续之前要完成，但在我继续之前。但PRICEA（）仍然是第一个然后PUSEB（）。

new Thread(() =>
                           {
                               new Thread(() =>
                               {
                                   PriceA = _service.GetPriceA();
                                   _waithandle[0].Set();
                               }).Start();

                               new Thread(() =>
                               {
                                   PriceB = _service.GetPriceB();
                                   _waithandle[1].Set();
                               }).Start();

                               WaitHandle.WaitAll(_waithandle);
                           }).Start();
Console.WriteLine("Hello");

.

我缺少什么？

更新：

private EventWaitHandle[] _waithandle;

.

ctor：

 _waithandle[0] = new ManualResetEvent(false);
 _waithandle[1] = new ManualResetEvent(false);

.

Answer 1

new Thread(() =>
                           {
                               new Thread(() =>
                               {
                                   _priceA = _service.GetPriceA();
                                   _waithandle[0].Set();
                               }).Start();

                               new Thread(() =>
                               {
                                   _priceB = _service.GetPriceB();
                                   _waithandle[1].Set();
                               }).Start();

                               WaitHandle.WaitAll(_waithandle);
                               PriceA = _priceA;
                               PriceB = _priceB;
                           }).Start();

This did the job for me. Culprit was the INotifyChangedProperty() of the PriceA and PriceB which updated the UI too early making my waitall redundant. In case someone else has a similar issue...

Answer 2

You're creating a separate thread to wait... but the code after the statement you've given will continue because you're not waiting in that thread. In other words, you're creating three threads:

• Thread X: Creates threads A and B, then waits for them to finish
• Thread A: Gets PriceA and then sets waitHandle[0]
• Thread B: Gets PriceB and then sets waitHandle[1]

But thread X is doing nothing after it's waited, so what's the point of waiting within it?

Additionally, it would be a lot simpler to just call Join on the extra threads that you've created. In fact, if you only need to wait in the "current" thread, you only need one extra thread in the first place:

Thread t = new Thread(() => { PriceA = _service.GetPriceA(); });
t.Start();
PriceB = _service.GetPriceB();
t.Join();
// Other code

By the time you reach "other code", both PriceA and PriceB will have been set. Of course, this is missing a considerable amount of error handling... but that's easier to add when you've got a simpler starting point than your currently over-complicated code.

Answer 3

Are you resetting correctly the _waithandle[0] and [1]? For example:

_waithandle[0] = new ManualResetEvent(false);
_waithandle[1] = new ManualResetEvent(false);