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如何在 C# 中进行只进、只读 WMI 查询？

发布于 2024-07-24 06:02:30 字数 69 浏览 3 评论 0原文

一位同事告诉我，如果我的 WMI 系统信息收集查询是只进和/或只读的，那么它们会更快。这就说得通了。但我该怎么做呢？

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皓月长歌 2024-07-31 06:02:30

您需要使用 EnumerationOptions 类并将其 Rewindable 属性设置为 false。下面是一个示例：

using System;
using System.Management;

namespace WmiTest
{
    class Program
    {
        static void Main()
        {
            EnumerationOptions options = new EnumerationOptions();
            options.Rewindable = false;
            options.ReturnImmediately = true;

            string query = "Select * From Win32_Process";

            ManagementObjectSearcher searcher =
                new ManagementObjectSearcher(@"root\cimv2", query, options);

            ManagementObjectCollection processes = searcher.Get();

            foreach (ManagementObject process in processes)
            {
                Console.WriteLine(process["Name"]);
            }

            // Uncomment any of these
            // and you will get an exception:

            //Console.WriteLine(processes.Count);

            /*
            foreach (ManagementObject process in processes)
            {
                Console.WriteLine(process["Name"]);
            }
            */
        }
    }
}

除非您使用它来枚举具有大量实例的类（如 Cim_DataFile），否则您不会看到任何性能改进，并且您只能枚举返回的 ManagementObjectCollection 一次。您也将无法使用 ManagementObjectCollection.Count 等。
至于只读查询，我不知道如何进行。

You need to use EnumerationOptions class and set its Rewindable property to false. Here is an example:

using System;
using System.Management;

namespace WmiTest
{
    class Program
    {
        static void Main()
        {
            EnumerationOptions options = new EnumerationOptions();
            options.Rewindable = false;
            options.ReturnImmediately = true;

            string query = "Select * From Win32_Process";

            ManagementObjectSearcher searcher =
                new ManagementObjectSearcher(@"root\cimv2", query, options);

            ManagementObjectCollection processes = searcher.Get();

            foreach (ManagementObject process in processes)
            {
                Console.WriteLine(process["Name"]);
            }

            // Uncomment any of these
            // and you will get an exception:

            //Console.WriteLine(processes.Count);

            /*
            foreach (ManagementObject process in processes)
            {
                Console.WriteLine(process["Name"]);
            }
            */
        }
    }
}

You won't see any performance improvement unless you use it to enumerate a class with a large number of instances (like Cim_DataFile) and you will get to enumerate the returned ManagementObjectCollection only once. You also won't be able to use ManagementObjectCollection.Count, etc.
As for read-only queries, I'm not sure how to make those.

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故笙诉离歌 2024-07-31 06:02:30

您的同事一定打算将半同步方法调用与仅向前枚举器一起使用。在半同步模式下，WMI 方法调用立即返回，对象在后台检索并在创建后按需返回。另外，当使用半同步模式检索大量实例时，建议获取只进枚举器以提高性能。这篇MSDN 文章。

正如 Uros 所指出的，要在半同步模式下获取只进枚举器，您需要使用 EnumerationOptions 类实例，并将 ReturnImmediately 属性设置为 true< /code> 并将 Rewindable 属性设置为 false，例如：

EnumerationOptions opt = new EnumerationOptions();
opt.ReturnImmediately = true;
opt.Rewindable = false;

ManagementObjectSearcher searcher = new ManagementObjectSearcher(scope, query, opt);

Your co-worker must have meant using the semisynchronous method calls together with forward-only enumerators. In the semisynchronous mode, WMI method calls return immediately and objects are retrieved in the background and returned on demand once they are created. Also, when using semisynchronous mode to retrieve a large number of instances, it is recommended to obtain forward-only enumerators to improve the performance. These peculiarities are explained in this MSDN article.

As Uros has pointed out, to get a forward-only enumerator in semisynchronous mode, you need to use the EnumerationOptions class instance with the ReturnImmediately property set to true and the Rewindable property set to false, e.g.:

EnumerationOptions opt = new EnumerationOptions();
opt.ReturnImmediately = true;
opt.Rewindable = false;

ManagementObjectSearcher searcher = new ManagementObjectSearcher(scope, query, opt);

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