Get Windows power plans/schemes in C# (using WinAPI)

Question

I'm interested in getting all power plans that you have in your computer using C#.

I was thinking you might be able to use the API PowerEnumerate function in some way:

DWORD WINAPI PowerEnumerate(
  _In_opt_   HKEY RootPowerKey,
  _In_opt_   const GUID *SchemeGuid,
  _In_opt_   const GUID *SubGroupOfPowerSettingsGuid,
  _In_       POWER_DATA_ACCESSOR AccessFlags,
  _In_       ULONG Index,
  _Out_opt_  UCHAR *Buffer,
  _Inout_    DWORD *BufferSize
);

But I have no idea on how to, as I really don't know C. How can I enumerate through all available power plans and create a a list of them? I then want to be able to access each power plans GUID and their "user friendly name".

Answer 1

This should do it:

using System;
using System.Linq;
using System.Reflection;
using System.Runtime.InteropServices;
using System.Collections.Generic;

public class Program
{
    [DllImport("PowrProf.dll")]
    public static extern UInt32 PowerEnumerate(IntPtr RootPowerKey, IntPtr SchemeGuid, IntPtr SubGroupOfPowerSettingGuid, UInt32 AcessFlags, UInt32 Index, ref Guid Buffer, ref UInt32 BufferSize);

    [DllImport("PowrProf.dll")]
    public static extern UInt32 PowerReadFriendlyName(IntPtr RootPowerKey, ref Guid SchemeGuid, IntPtr SubGroupOfPowerSettingGuid, IntPtr PowerSettingGuid, IntPtr Buffer, ref UInt32 BufferSize);

    public enum AccessFlags : uint
    {
        ACCESS_SCHEME = 16,
        ACCESS_SUBGROUP = 17,
        ACCESS_INDIVIDUAL_SETTING = 18
    }

    private static string ReadFriendlyName(Guid schemeGuid)
    {
        uint sizeName = 1024;
        IntPtr pSizeName = Marshal.AllocHGlobal((int)sizeName);

        string friendlyName;

        try
        {
            PowerReadFriendlyName(IntPtr.Zero, ref schemeGuid, IntPtr.Zero, IntPtr.Zero, pSizeName, ref sizeName);
            friendlyName = Marshal.PtrToStringUni(pSizeName);
        }
        finally
        {
            Marshal.FreeHGlobal(pSizeName);
        }

        return friendlyName;
    }

    public static IEnumerable<Guid> GetAll()
    {
        var schemeGuid = Guid.Empty;

        uint sizeSchemeGuid = (uint)Marshal.SizeOf(typeof(Guid));
        uint schemeIndex = 0;

        while (PowerEnumerate(IntPtr.Zero, IntPtr.Zero, IntPtr.Zero, (uint)AccessFlags.ACCESS_SCHEME, schemeIndex, ref schemeGuid, ref sizeSchemeGuid) == 0)
        {
            yield return schemeGuid;
            schemeIndex++;
        }
    }

    public static void Main()
    {   
        var guidPlans = GetAll();

        foreach (Guid guidPlan in guidPlans)
        {
            Console.WriteLine(ReadFriendlyName(guidPlan));
        }
    }
}

You might have to run this program as administrator for security purposes.