protected unsafe void EnableActionFreeFormQuery()
        {
            iCallbackFreeFormQuery = new CallbackFreeFormQuery(DoFreeFormQuery);
            IntPtr ptr = GCHandle.ToIntPtr(iGch);

            DvServiceUpnpOrgContentDirectory3EnableActionFreeFormQuery(iHandle, iCallbackFreeFormQuery, ptr);
        }
 static extern void DvServiceUpnpOrgContentDirectory3EnableActionFreeFormQuery(uint aHandle, CallbackFreeFormQuery aCallback, IntPtr aPtr);