BlockingCollection< T> TryTake（）返回假？ [英] When can BlockingCollection<T> TryTake() return false?

问题描述

假设BlockingCollection在下面使用ConcurrentQueue，何时 TryTake（T，Int32）方法如果使用的是Timeout.Infinite，则返回false。

Assuming the BlockingCollection is using a ConcurrentQueue underneath, when could the TryTake(T, Int32) method return false if you are using Timeout.Infinite?

推荐答案

这是一个简单的示例，它显示何时可以返回false：当集合被标记为 CompleteAdding 并成为空容器时

Here's a simple example that shows when it can return false: when the collection is marked as CompleteAdding and becomes emptу

//by default, BlockingCollection will use ConcurrentQueue
BlockingCollection<int> coll = new BlockingCollection<int>();

coll.Add(1);
coll.Add(2);
coll.CompleteAdding();

int item;

if (coll.TryTake(out item, -1))
{
    Console.WriteLine(item);
}

if (coll.TryTake(out item, -1))
{
    Console.WriteLine(item);
}

if (coll.TryTake(out item, -1))
{
    //this won't get hit
}
else
{
    Console.WriteLine("TryTake returned false!");
}

这可让您禁止在队列中添加新项目并禁止剩余元素的完整处理

This allows you to forbid adding new items in queue and complete processing of remaining elements

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