C# Parallel.Foreach 未对列表中的所有项目执行操作

Question

    public static void RemoveAllNetworkPrinters()
    {
        ManagementScope oManagementScope = new ManagementScope(ManagementPath.DefaultPath);
        oManagementScope.Connect();

        SelectQuery oSelectQuery = new SelectQuery();
        oSelectQuery.QueryString = @"SELECT * FROM Win32_Printer WHERE ServerName IS NOT NULL";

        using (ManagementObjectSearcher oObjectSearcher = new ManagementObjectSearcher(oManagementScope, oSelectQuery))
        {
            using (ManagementObjectCollection oObjectCollection = oObjectSearcher.Get())
            {
                if (oObjectCollection.Count != 0)
                {
                    foreach (ManagementObject oItem in oObjectCollection)
                    {
                        oItem.Delete();

                    }
                }
            }
        }
    }

    public static void RemoveAllNetworkPrintersParallel()
    {
        ManagementScope oManagementScope = new ManagementScope(ManagementPath.DefaultPath);
        oManagementScope.Connect();

        SelectQuery oSelectQuery = new SelectQuery();
        oSelectQuery.QueryString = @"SELECT * FROM Win32_Printer WHERE ServerName IS NOT NULL";

        using (ManagementObjectSearcher oObjectSearcher = new ManagementObjectSearcher(oManagementScope, oSelectQuery))
        {
            using (ManagementObjectCollection oObjectCollection = oObjectSearcher.Get())
            {
                if (oObjectCollection.Count != 0)
                {
                    Parallel.ForEach(oObjectCollection.OfType<ManagementObject>().ToList(), oItem =>
                    {
                        oItem.Delete();
                    });
                }
            }
        }
    }

我有一个关于 c# 中 Parallel.Foreach 的问题。我一直在测试并在我为测试目的提供的示例中看到一些奇怪的东西。当我执行此功能的非并行版本时，它工作正常，但当我执行并行版本时，1-2 个项目之间的任何地方都不会在我循环通过的列表中处理。我已经阅读了 msdn 文档，但这里一定遗漏了一些东西。我知道您不能保证订单商品会得到处理，但您认为可以保证列表中的所有商品都会得到处理吗？任何有助于理解或我做错了什么的帮助将不胜感激。谢谢

Answer 1

如评论中所述，ManagementObject.Delete() 不是线程安全操作，因此您不应在不同线程中使用它 MSDN

Any public static ( Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

但是如果你真的需要这样做并且你想在那里使用lock，你可以像这样

var lockObject = new Object();

Parallel.ForEach(/*.....*/, item =>
{
    lock (lockObject)
    {
        // do your magic here
    }
});

但正如我所说 使用此代码没有意义，因为它比序号 foreach.

慢

所以，我的建议是只使用 foreach。

C# Parallel.Foreach 未对列表中的所有项目执行操作

C# Parallel.Foreach that is not peforming action on all items in list

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