Foreach 循环和带锁定的变量 [英] Foreach loop and variables with locking

问题描述

基本上我想做的是这个伪代码

Basically what I want to do is this psuedo code

List<DatabaseRecord> records;

List<ChangedItem> changedItems;

Parallel.ForEach<DatabaseRecord>(records, (item, loopState) =>
{
    if (item.HasChanged)
    {
        lock (changedItems)
        {
            changedItems.Add(new ChangedItem(item));
        }
    }
});

但我担心的是锁定已更改的项目.虽然它有效，但我听说它必须一遍又一遍地序列化锁定的对象.有没有更好的方法来做到这一点?

But what I'm worried about is locking on the changedItems. While it works, I have heard that it has to serialize the locked object over and over. Is there a better way of doing this?

推荐答案

你可以为你的 changedItems 使用 ConcurrentCollection.像 ConcurrentQueue 这样的东西?那么你根本不需要锁定.

Could you use a ConcurrentCollection for your changedItems. Something like ConcurrentQueue? Then you wouldn't need to lock at all.

更新:

关于 ConcurrentQueue，Enqueue 不会阻塞线程以保证操作线程安全.它通过 SpinWait 保持在用户模式...

With regard to the ConcurrentQueue, the Enqueue won't block the thread in keeping the operation thread safe. It stays in user mode with a SpinWait...

public void Enqueue(T item)
{
    SpinWait wait = new SpinWait();
    while (!this.m_tail.TryAppend(item, ref this.m_tail))
    {
        wait.SpinOnce();
    }
}

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