Using an API Function -> SetupDiGetClassDevs ?

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

Code:

---

[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

The problem is with

Code:

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

---

Find out the actual GUID and put that into the string.

Darwen.