我是否需要使用 try catch 或检查 ThreadPool.QueueUserWorkItem 的 return 值

Question

上述方法的文档对其 return 类型说明如下：

true if the method is successfully queued; NotSupportedException is thrown if the work item could not be queued.

这是否意味着该函数永远不会 return 为假？但是抛出呢？如果是这样，那为什么要有 return 类型呢？我会说，或 return true/false WorkItem 是否已排队，或者类型为 void 并在 WorkItem 无法排队时抛出。

我知道有这个duplicate question，但在我看来它确实不是很确定的答案。

Answer 1

您需要仔细阅读文档。虽然 MSDN 指出：

true if the method is successfully queued; NotSupportedException is thrown if the work item could not be queued.

...下面还说：

NotSupportedException: The common language runtime (CLR) is hosted, and the host does not support this action.

我的意思是，如果托管环境不支持线程池，将抛出 NotSupportedException。

因此，如果您在可以的地方对线程进行排队，则不需要 try/catch 块。至少，您可以使用常规布尔值 return 检查线程是否可以排队。

Answer 2

Does that mean that the function never returns false? But throws instead? If so, then why have a return type at all

Lets look at the source code:

//ThreadPool has per-appdomain managed queue of work-items. The VM is
//responsible for just scheduling threads into appdomains. After that
//work-items are dispatched from the managed queue.
[System.Security.SecurityCritical]  // auto-generated
private static bool QueueUserWorkItemHelper(
    WaitCallback callBack, Object state, ref StackCrawlMark stackMark, bool compressStack)
{
    bool success =  true;

    if (callBack != null)
    {
        //The thread pool maintains a per-appdomain managed work queue.
        //New thread pool entries are added in the managed queue.
        //The VM is responsible for the actual growing/shrinking of 
        //threads. 

        EnsureVMInitialized();

        // If we are able to create the workitem, 
        // we need to get it in the queue without being interrupted
        // by a ThreadAbortException.
        //
        try { }
        finally
        {
            QueueUserWorkItemCallback tpcallBack = new QueueUserWorkItemCallback(
                                        callBack, state, compressStack, ref stackMark);
            ThreadPoolGlobals.workQueue.Enqueue(tpcallBack, true);
            success = true;
        }
    }
    else
    {
        throw new ArgumentNullException("WaitCallback");
    }
    return success;
}

似乎成功将真正 return true，因为它最初是在排队项目之前设置的，或者在运行time 无法排队的情况下抛出异常代表。

Any better ideas?

这对我来说似乎是多余的，除非您真的不信任运行-time 环境并且不确定它是否提供底层线程池机制。否则，如果您使用的是 Microsoft 的运行-time，则只需使用原始的 QueueUserWorkItem.

就可以了

我是否需要使用 try catch 或检查 ThreadPool.QueueUserWorkItem 的 return 值

Do I need to use try catch or check the return value of ThreadPool.QueueUserWorkItem

.net

c#

multithreading

threadpool