I have a C dll which interfaces to a voice card. The function call requires a special structure to be passed. I am attempting to wrap the C dll in a C# class so I can use C# instead of C.

The C structure is as follows:

typedef struct
{
TCASGroupIndex firstGroupIndex; /* Index of first CAS channel group. */
PK_U32 numberOfGroups; /* Number of CAS channel group. */
PK_U32 isDigitalLogging;
} TCASGroupInfo;

The C function call is as follows:
PK_STATUS WINAPI PK_CAS_GetCASGroupInfo ( IN TBoardIndex boardID, OUT TCASGroupInfo* info);

The data types are defined as follows:
typedef unsigned           PK_BOOL;   Unsigned boolean type.
typedef char                  PK_CHAR,*PK_PCHAR;   Standard char type.
typedef unsigned char    PK_U8,*PK_PU8;   8-bit unsigned char type.
typedef signed char        PK_I8,*PK_PI8;   8-bit signed char type.
typedef unsigned short   PK_U16,*PK_PU16;   Unsigned short 16-bit type.
typedef signed short       PK_I16,*PK_PI16;   Signed short 16-bit type.
typedef unsigned long    PK_U32,*PK_PU32;   Unsigned long 32-bit long type.
typedef signed long        PK_I32,*PK_PI32;   Signed long 32-bit long type.
typedef double              PK_REAL,*PK_PREAL;   64-bit long real type.
typedef unsigned           PK_WORD,*PK_PWORD;   Unsigned type.
typedef unsigned           PK_UINT,*PK_PUINT;   Unsigned type.
typedef signed              PK_INT,*PK_PINT;   Signed type.
typedef void                  PK_VOID,*PK_PVOID;   Void type.
typedef int                    PK_STATUS;   Common status return code.
typedef unsigned long   TDeviceHandle,*PDeviceHandle;   DSP device handle type.
typedef unsigned long   TResourceHandle,*PResourceHandle;   Analog trunk, phone and DSP port resource handle type.

typedef PK_U32 TEventId,*PEventId;   Event ID type in event handler function.
typedef PK_WORD TBoardIndex;   Board index type.
typedef PK_WORD TSwitchIndex;   Switch index type.
typedef PK_U16 TDSPIndex;   DSP index type.
typedef PK_U16 TSpanIndex;   Span index type.
typedef PK_WORD TSwitchStream, *PSwitchStream;   Switch stream type.
typedef PK_WORD TSwitchTimeslot, *PSwitchTimeslot;   Switch timeslot type.
typedef PK_U32 TResourceMask, *PResourceMask;   Resource mask type.
typedef PK_WORD TSwitchPattern, *PSwitchPattern;   Switch pattern type.
typedef PK_INT TGainLevel,*PGainLevel;   Gain level type.
typedef PK_U32 TTimeDuration,*PTimeDuration;   Time duration type.

My Interop function is as follows:
[DllImport("H:\\PIKA\\Debug\\PikaAPI.dll", EntryPoint="PK_CAS_GetCASGroupInfo", CallingConvention=CallingConvention.StdCall)]
public static extern int CASGroupInfo(int nBoard, ref TCASGroupInfo groupInfo);

public int GetCASGroupInfo(int nBoard, ref TCASGroupInfo groupInfo)
{
        return CASGroupInfo( nBoard, ref groupInfo );
}

I get the following error:

Cannot marshal parameter #2: The type definition of this type has no layout information.

What's the proper syntax to make my function call work properly?

Thanks.

Tim Gaither
MSDN Subscriber