Using an API Function -> SetupDiGetClassDevs ?

[M-Dayyan]

Hi.
I'm using SetupDiGetClassDevs function in my App.
This is my snippet code , but it's wrong
and this Exception is occurring .

[DllImport("setupapi.dll", CharSet = CharSet.Auto)]
static extern IntPtr SetupDiGetClassDevs( 
   ref Guid ClassGuid,
   IntPtr Enumerator,
   IntPtr hwndParent,
   int Flags
);

static Guid DiskGUID = new Guid("GUID_DEVINTERFACE_DISK");

static void Main(string[] args)
{
    IntPtr h = SetupDiGetClassDevs(ref DiskGUID, IntPtr.Zero, IntPtr.Zero, 1);

    //Console.WriteLine(h);
    Console.ReadKey();
}

Would you guide me how I can use it ?
Thanks