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powerenumerate (powrprof)
 
.
Summary
Enumerates the specified elements in a power scheme. This function is normally called in a loop incrementing the Index parameter to retrieve subkeys until they've all been enumerated.

C# Signature:

[DllImport("powrprof.dll", SetLastError=true)]
static extern uint PowerEnumerate(IntPtr RootPowerKey,
                     IntPtr SchemeGuid,
                     IntPtr SubGroupOfPowerSettingsGuid,
                     PowerDataAccessor AccessFlags,
                     uint Index,
                     IntPtr Buffer,
                     ref uint BufferSize);

enum PowerDataAccessor : uint
{
   ACCESS_AC_POWER_SETTING_INDEX = 0,
   ACCESS_DC_POWER_SETTING_INDEX = 1,
   ACCESS_SCHEME = 16,
   ACCESS_SUBGROUP = 17,
   ACCESS_INDIVIDUAL_SETTING = 18,
   ACCESS_ACTIVE_SCHEME = 19,
   ACCESS_CREATE_SCHEME = 20
}

VB Signature:

Declare Function PowerEnumerate Lib "powrprof.dll" (TODO) As TODO

User-Defined Types:

None.

Alternative Managed API:

Do you know one? Please contribute it!

Notes:

Use EnumPwrSchemes for Windows versions prior to Vista.

Tips & Tricks:

Please add some!

Sample Code:

List<Guid> GUIDs = new List<Guid>();

IntPtr ReadBuffer;
uint BufferSize = 16;

uint Index = 0;
uint ReturnCode = 0;

while (ReturnCode == 0)
{
   ReadBuffer = Marshal.AllocHGlobal((int)BufferSize);

   try
   {
     ReturnCode = PowerEnumerate(IntPtr.Zero, IntPtr.Zero, IntPtr.Zero, PowerDataAccessor.ACCESS_SCHEME, Index, ReadBuffer, ref BufferSize);

     if (ReturnCode == 259) break; // no more data
     if (ReturnCode != 0)
     {
       throw new COMException("Error occurred while enumerating power schemes. Win32 error code: " + ReturnCode);
     }

     Guid NewGuid = (Guid) Marshal.PtrToStructure(ReadBuffer, typeof(Guid));
     GUIDs.Add(NewGuid);
   }
   finally
   {
     Marshal.FreeHGlobal(ReadBuffer);
   }

   Index++;
}

// now we have a list of identifiers for all the power schemes on the system,
// we can pass those into other powrprof methods to retrieve more information on each

Documentation

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