gps turn of when device into the power off mode

Code Snippet
const string GPS_DEVICE_NAME_PATH = "DRIVERS\\Builtin\\GPSID";

public string GpsDeviceName

{

   get

   {

     if (_gpsDeviceName == null)

     {

       RegistryKey gpsInfoKey = Registry.LocalMachine.OpenSubKey(GPS_DEVICE_NAME_PATH);

       if (gpsInfoKey != null)

       {

         try

         {

           _gpsDeviceName = String.Format("{0}{1}:", gpsInfoKey.GetValue("Prefix"),    gpsInfoKey.GetValue("Index"));

         }

         catch { }

       }

     }

     return _gpsDeviceName;

   }

}



private void Form1_Load(object sender, EventArgs e)

{

   CoreDLL.PowerPolicyNotify(PPNMessage.PPN_UNATTENDEDMODE, -1);

   CoreDLL.GetDevicePower(GpsDeviceName, DevicePowerFlags.POWER_NAME, out currentPowerState);

   _gpsPowerRequirements = CoreDLL.SetPowerRequirement(GpsDeviceName, CEDEVICE_POWER_STATE.D0,  DevicePowerFlags.POWER_NAME, IntPtr.Zero, 0);



}

private void Form1_Closing(object sender, CancelEventArgs e)

{

   _gpsDevice.Close();

   CoreDLL.PowerPolicyNotify(PPNMessage.PPN_UNATTENDEDMODE, 0);

   CoreDLL.ReleasePowerRequirement(_gpsPowerRequirements);

}