Thread: passing nullable type to a P/invoked function

Does anyone know of a way I can pass a nullable type to a p/invoked function? specifically I need parameter 1 of:

Code:

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

to be passable so I can avoid have to overload the function.

Originally Posted by valaris

SetupDiGetClassDevs

From looking at that I'd use the signature below and pass IntPtr.Zero for NULL.

Code:

[DllImport("setupapi.dll", CharSet = CharSet.Auto)]
static extern IntPtr SetupDiGetClassDevs(           // 1st form using a ClassGUID
   ref Guid ClassGuid,
   IntPtr Enumerator,
   IntPtr hwndParent,
   int Flags
);

I meant parameter 1 of the function. not the enumerator the ref Guid ClassGuid variable. Also I should say I changed the enumerator to string type variable. The original posting of the function was a typo.