并发集合上的linq操作线程安全吗? [英] Are linq operations on concurrent collections thread safe?

问题描述

例如，以下代码线程安全:

For example is the following code thread safe:

ConcurrentQueue<Guid> _queue = new ConcurrentQueue<Guid>();
while(true)
{
for(int y = 0; y < 3; y++)
{
    if(y % 3 == 0)
    {
    System.Threading.Tasks.Task.Run(() => _queue.Enqueue(Guid.NewGuid()));
    }
    else if (y % 3 == 1)
    {
    Guid x;
    System.Threading.Tasks.Task.Run(() => _queue.TryDequeue(out x));
    }
    else if(y % 3 == 2)
    {
    System.Threading.Tasks.Task.Run(() =>
    {
        if (_queue.Any(t => t == testGuid))
        {
        // Do something
        }
    });

    }
}

显然标题不够清晰，因此更新了代码示例以包含实际的多线程行为，是的，上面的代码只是多线程行为的 sample .

Apparently the title wasn't clear enough so updated the code sample to include actual multi threaded behaviour, yes the code above is just a sample of multi-threaded behaviour.

推荐答案

LINQ操作是只读的，因此它们在 all 集合上是线程安全的.当然，如果您添加修改Where或Select方法内部集合的代码，它们将不再是线程安全的.

LINQ operations are read-only so they are thread safe on all collections. Of course, if you add code that modifies a collection inside the Where or Select method, they cease to be thread-safe.

线程安全的集合确保修改是线程安全的，这在执行LINQ查询时并不是真正的问题.

Thread-safe collections ensure that modifications are thread-safe, which isn't really a concern when executing a LINQ query.

在遍历期间修改集合是不安全的.普通集合在修改迭代器时会使迭代器无效，而线程安全集合不会使迭代器无效.在某些情况下(例如在ConcurrentQueue中)，这是通过在迭代过程中呈现数据快照来实现的.

What isn't safe is modifying a collection during traversal. Normal collections invalidate iterators when they are modified, while the thread-safe collections do not. In some cases, (eg in ConcurrentQueue) this is achieved by presenting a snapshot of the data during iteration.

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