如何使用电源管理功能 (PowerEnuimerate) 获取电源设置答案

【问题标题】：How to use Power Management Functions (PowerEnuimerate) to get power settings如何使用电源管理功能 (PowerEnuimerate) 获取电源设置
【发布时间】：2013-04-08 02:04:56
【问题描述】：

我需要我的应用程序读取诸如系统在关闭显示器、进入睡眠状态或进入休眠状态之前等待的时间。据我所知，我需要使用电源管理功能 (http://msdn.microsoft.com/en-us/library/aa373163%28v=vs.85%29.aspx) 特别是，我似乎需要使用 PowerEnumerate 方法 (http://msdn.microsoft.com/en-us/library/aa372730%28v=vs.85%29.aspx)。

我真的很困惑如何做到这一点。首先，我在 C# 中执行此操作，代码看起来是 C++。其次，C++ 代码似乎并没有真正告诉你如何具体读取我想要的不同超时时间。

注意，我是 Windows 编程和 C# 的新手。我的大部分经验都是在 Java 和 Android 方面的。

谢谢

【问题讨论】：

标签： c# .net windows desktop

【解决方案1】：

我找到了一个example on MSDN 用于在VB 中使用PowerEnumerate 函数。

我已将示例转换为 C#，并将友好名称添加到循环中每个视频设置的输出中。您可以将GUID_VIDEO_SUBGROUP 更改为其他子组之一以查看其他设置。

using System;
using System.ComponentModel;
using System.Runtime.InteropServices;
using System.Text;

namespace TestProject
{
    class PowerEnumerator
    {
        private static Guid NO_SUBGROUP_GUID = new Guid("fea3413e-7e05-4911-9a71-700331f1c294");
        private static Guid GUID_DISK_SUBGROUP = new Guid("0012ee47-9041-4b5d-9b77-535fba8b1442");
        private static Guid GUID_SYSTEM_BUTTON_SUBGROUP = new Guid("4f971e89-eebd-4455-a8de-9e59040e7347");
        private static Guid GUID_PROCESSOR_SETTINGS_SUBGROUP = new Guid("54533251-82be-4824-96c1-47b60b740d00");
        private static Guid GUID_VIDEO_SUBGROUP = new Guid("7516b95f-f776-4464-8c53-06167f40cc99");
        private static Guid GUID_BATTERY_SUBGROUP = new Guid("e73a048d-bf27-4f12-9731-8b2076e8891f");
        private static Guid GUID_SLEEP_SUBGROUP = new Guid("238C9FA8-0AAD-41ED-83F4-97BE242C8F20");
        private static Guid GUID_PCIEXPRESS_SETTINGS_SUBGROUP = new Guid("501a4d13-42af-4429-9fd1-a8218c268e20");

        [DllImport("powrprof.dll")]
        static extern uint PowerEnumerate(
            IntPtr RootPowerKey,
            IntPtr SchemeGuid,
            ref Guid SubGroupOfPowerSetting,
            uint AccessFlags,
            uint Index,
            ref Guid Buffer,
            ref uint BufferSize);

        [DllImport("powrprof.dll")]
        static extern uint PowerGetActiveScheme(
            IntPtr UserRootPowerKey,
            ref IntPtr ActivePolicyGuid);

        [DllImport("powrprof.dll")]
        static extern uint PowerReadACValue(
            IntPtr RootPowerKey,
            IntPtr SchemeGuid,
            IntPtr SubGroupOfPowerSettingGuid,
            ref Guid PowerSettingGuid,
            ref int Type,
            ref IntPtr Buffer,
            ref uint BufferSize
            );

        [DllImport("powrprof.dll", CharSet = CharSet.Unicode)]
        static extern uint PowerReadFriendlyName(
            IntPtr RootPowerKey,
            IntPtr SchemeGuid,
            IntPtr SubGroupOfPowerSettingGuid,
            IntPtr PowerSettingGuid,
            StringBuilder Buffer,
            ref uint BufferSize
            );

        [DllImport("kernel32.dll")]
        static extern IntPtr LocalFree(
            IntPtr hMem
            );

        private const uint ERROR_MORE_DATA = 234;

        public static void GetCurrentPowerEnumerateVistaAPI()
        {
            IntPtr activeGuidPtr = IntPtr.Zero;
            try
            {
                uint res = PowerGetActiveScheme(IntPtr.Zero, ref activeGuidPtr);
                if (res != 0)
                    throw new Win32Exception();

                //Get Friendly Name
                uint buffSize = 0;
                StringBuilder buffer = new StringBuilder();
                Guid subGroupGuid = Guid.Empty;
                Guid powerSettingGuid = Guid.Empty;
                res = PowerReadFriendlyName(IntPtr.Zero, activeGuidPtr,
                    IntPtr.Zero, IntPtr.Zero, buffer, ref buffSize);

                if (res == ERROR_MORE_DATA)
                {
                    buffer.Capacity = (int)buffSize;
                    res = PowerReadFriendlyName(IntPtr.Zero, activeGuidPtr,
                        IntPtr.Zero, IntPtr.Zero, buffer, ref buffSize);
                }

                if (res != 0)
                    throw new Win32Exception();

                Console.WriteLine("ReadFriendlyName = " +
                    buffer.ToString());

                //Get the Power Settings
                Guid VideoSettingGuid = Guid.Empty;
                uint index = 0;
                uint BufferSize = Convert.ToUInt32(Marshal.SizeOf(typeof(Guid)));

                while (
                    PowerEnumerate(IntPtr.Zero, activeGuidPtr, ref GUID_VIDEO_SUBGROUP,
                    18, index, ref VideoSettingGuid, ref BufferSize) == 0)
                {
                    uint size = 4;
                    IntPtr temp = IntPtr.Zero;
                    int type = 0;
                    res = PowerReadACValue(IntPtr.Zero, activeGuidPtr, IntPtr.Zero,
                        ref VideoSettingGuid, ref type, ref temp, ref size);

                    IntPtr pSubGroup = Marshal.AllocHGlobal(Marshal.SizeOf(GUID_VIDEO_SUBGROUP));
                    Marshal.StructureToPtr(GUID_VIDEO_SUBGROUP, pSubGroup, false);
                    IntPtr pSetting = Marshal.AllocHGlobal(Marshal.SizeOf(VideoSettingGuid));
                    Marshal.StructureToPtr(VideoSettingGuid, pSetting, false);

                    uint builderSize = 200;
                    StringBuilder builder = new StringBuilder((int)builderSize);
                    res = PowerReadFriendlyName(IntPtr.Zero, activeGuidPtr,
                        pSubGroup, pSetting, builder, ref builderSize);
                    Console.WriteLine(builder.ToString() + " = " + temp.ToString());

                    index++;
                }
            }
            finally
            {
                if (activeGuidPtr != IntPtr.Zero)
                {
                    IntPtr res = LocalFree(activeGuidPtr);
                    if (res != IntPtr.Zero)
                        throw new Win32Exception();
                }
            }
        }
    }
}

此代码的结果输出：

【讨论】：

看起来我们正在使用一堆 .dll。我在哪里可以找到有关它们的文档？
根据MSDN PowerEnumerate page（见页面底部），powrprof.dll 似乎包含在较新版本的 Windows（Vista 和较新版本）中，并且 kernel32.dll（LocalFree 函数）已成为其中的一部分至少从 XP 开始的 Windows：LocalFree on MSDN
我正在尝试示例代码，但我注意到当我在“电源选项”对话框中更改单个设置时。当我重新运行示例时，它不会反映出来。例如，我在 Balanced 计划中，我将“最小处理器状态”从 5% 更改为 100%，但输出将始终显示 5%。这有什么原因吗？如何获得正确的值？

【解决方案2】：

但是接受的答案仍然有效，我想指出其中存在一个错误，导致它枚举所有默认值而不是实际值。

读取 AC 值时，还需要传递子组 guid：

res = PowerReadACValue(IntPtr.Zero, activeGuidPtr, pSubGroup, ref settingGuid, ref type, ref temp, ref size);

【讨论】：

【解决方案3】：

我偶然发现这篇文章寻找类似的解决方案，并发现并纠正了一些错误。

我的 IDE（Visual Studio 2019）需要一个主函数，所以我必须弄清楚这个相当复杂的代码应该在哪里。最后我尝试将GetCurrentPowerEnumerateVistaAPI() 重命名为Main()。我还加入了@Martijn Spaan 修复程序，稍作改动。而不是ref settingGuid 添加ref videoSettingGuid。

所以现在它看起来像这样并且按预期运行：

using System;
using System.ComponentModel;
using System.Runtime.InteropServices;
using System.Text;

namespace TestProject
{
    class PowerEnumerator
    {
        private static Guid NO_SUBGROUP_GUID = new Guid("fea3413e-7e05-4911-9a71-700331f1c294");
        private static Guid GUID_DISK_SUBGROUP = new Guid("0012ee47-9041-4b5d-9b77-535fba8b1442");
        private static Guid GUID_SYSTEM_BUTTON_SUBGROUP = new Guid("4f971e89-eebd-4455-a8de-9e59040e7347");
        private static Guid GUID_PROCESSOR_SETTINGS_SUBGROUP = new Guid("54533251-82be-4824-96c1-47b60b740d00");
        private static Guid GUID_VIDEO_SUBGROUP = new Guid("7516b95f-f776-4464-8c53-06167f40cc99");
        private static Guid GUID_BATTERY_SUBGROUP = new Guid("e73a048d-bf27-4f12-9731-8b2076e8891f");
        private static Guid GUID_SLEEP_SUBGROUP = new Guid("238C9FA8-0AAD-41ED-83F4-97BE242C8F20");
        private static Guid GUID_PCIEXPRESS_SETTINGS_SUBGROUP = new Guid("501a4d13-42af-4429-9fd1-a8218c268e20");

        [DllImport("powrprof.dll")]
        static extern uint PowerEnumerate(
            IntPtr RootPowerKey,
            IntPtr SchemeGuid,
            ref Guid SubGroupOfPowerSetting,
            uint AccessFlags,
            uint Index,
            ref Guid Buffer,
            ref uint BufferSize);

        [DllImport("powrprof.dll")]
        static extern uint PowerGetActiveScheme(
            IntPtr UserRootPowerKey,
            ref IntPtr ActivePolicyGuid);

        [DllImport("powrprof.dll")]
        static extern uint PowerReadACValue(
            IntPtr RootPowerKey,
            IntPtr SchemeGuid,
            IntPtr SubGroupOfPowerSettingGuid,
            ref Guid PowerSettingGuid,
            ref int Type,
            ref IntPtr Buffer,
            ref uint BufferSize
            );

        [DllImport("powrprof.dll", CharSet = CharSet.Unicode)]
        static extern uint PowerReadFriendlyName(
            IntPtr RootPowerKey,
            IntPtr SchemeGuid,
            IntPtr SubGroupOfPowerSettingGuid,
            IntPtr PowerSettingGuid,
            StringBuilder Buffer,
            ref uint BufferSize
            );

        [DllImport("kernel32.dll")]
        static extern IntPtr LocalFree(
            IntPtr hMem
            );

        private const uint ERROR_MORE_DATA = 234;

        public static void Main()
        //public static void GetCurrentPowerEnumerateVistaAPI()
        {
            IntPtr activeGuidPtr = IntPtr.Zero;
            try
            {
                uint res = PowerGetActiveScheme(IntPtr.Zero, ref activeGuidPtr);
                if (res != 0)
                    throw new Win32Exception();

                //Get Friendly Name
                uint buffSize = 0;
                StringBuilder buffer = new StringBuilder();
                Guid subGroupGuid = Guid.Empty;
                Guid powerSettingGuid = Guid.Empty;
                res = PowerReadFriendlyName(IntPtr.Zero, activeGuidPtr,
                    IntPtr.Zero, IntPtr.Zero, buffer, ref buffSize);

                if (res == ERROR_MORE_DATA)
                {
                    buffer.Capacity = (int)buffSize;
                    res = PowerReadFriendlyName(IntPtr.Zero, activeGuidPtr,
                        IntPtr.Zero, IntPtr.Zero, buffer, ref buffSize);
                }

                if (res != 0)
                    throw new Win32Exception();

                Console.WriteLine("ReadFriendlyName = " +
                    buffer.ToString());

                //Get the Power Settings
                Guid VideoSettingGuid = Guid.Empty;
                uint index = 0;
                uint BufferSize = Convert.ToUInt32(Marshal.SizeOf(typeof(Guid)));

                while (
                    PowerEnumerate(IntPtr.Zero, activeGuidPtr, ref GUID_VIDEO_SUBGROUP,
                    18, index, ref VideoSettingGuid, ref BufferSize) == 0)
                {
                    uint size = 4;
                    IntPtr temp = IntPtr.Zero;
                    int type = 0;

                    // My chenges
                    IntPtr pSubGroup = Marshal.AllocHGlobal(Marshal.SizeOf(GUID_VIDEO_SUBGROUP));
                    res = PowerReadACValue(IntPtr.Zero, activeGuidPtr, pSubGroup, ref VideoSettingGuid, ref type, ref temp, ref size);
                    // end my changes

                    Marshal.StructureToPtr(GUID_VIDEO_SUBGROUP, pSubGroup, false);
                    IntPtr pSetting = Marshal.AllocHGlobal(Marshal.SizeOf(VideoSettingGuid));
                    Marshal.StructureToPtr(VideoSettingGuid, pSetting, false);

                    uint builderSize = 200;
                    StringBuilder builder = new StringBuilder((int)builderSize);
                    res = PowerReadFriendlyName(IntPtr.Zero, activeGuidPtr,
                        pSubGroup, pSetting, builder, ref builderSize);
                    Console.WriteLine(builder.ToString() + " = " + temp.ToString());

                    index++;
                }
            }
            finally
            {
                if (activeGuidPtr != IntPtr.Zero)
                {
                    IntPtr res = LocalFree(activeGuidPtr);
                    if (res != IntPtr.Zero)
                        throw new Win32Exception();
                }
            }
            Console.ReadLine();
        }
    }
}

【讨论】：