C / C++ / MFC

struct SLEDFrame {
	BYTE idtfr;
	BYTE Data1;
	BYTE Data2;
};

SLEDFrame btnLED[] = {
	{ 0x53, 0x30, 0x30 }, 					
	{ 0x53, 0x30, 0x31 },  			
	{ 0x53, 0x30, 0x32 },  			
	{ 0x53, 0x30, 0x33 },  			
	{ 0x53, 0x30, 0x34 },  		
	{ 0x53, 0x30, 0x35 }, 
}

void CMSCOMMDlg::setLED(int pLEDNo, BOOL pState) {
	BYTE bState;
	if (pState) {
		bState = 0x31;   //ON
	} else  {
		bState = 0x30;   //OFF
	}
	BYTE bID = btnLED[pLEDNo-1].idtfr;
	BYTE bByte1 = btnLED[pLEDNo-1].Data1;
	BYTE bByte2 = btnLED[pLEDNo-1].Data2;
	BYTE bSum = bByte1 + bByte2 + bState; 	
	BYTE bCheckSumByte1 = 0x30 | (bSum >> 4);
	BYTE bCheckSumByte2 = 0x30 | (bSum & 0x0F);
	
	//To send data use this code:
	CByteArray btArray;
	btArray.Add(bID); 	  //Identifier byte
	btArray.Add(bByte1); // DataByte 1
	btArray.Add(bByte2); // DataByte 2
	btArray.Add(bState); //Status Byte
	btArray.Add(bCheckSumByte1); //CheckSumByte1
	btArray.Add(bCheckSumByte2); //CheckSumByte2
	
	COleVariant var(btArray);
	m_Comm.SetOutput(var);	// Send the data.
}

CString strNumber = "0x30h"; //this will work with or without the 'h'
BYTE nNumber = (BYTE)strtol(((LPCSTR)strNumber) + 2, NULL, 16);

// All the following functions are exported from a DLL.
 
Stuff* MakeSomeCrap()
{
    Stuff *pStuff = new Stuff();
    return pStuff;
}
 
void FreeStuff(Stuff *pStuff)
{
    // Since the same DLL delete's it we know for sure we're using the correct heap.
    delete pStuff;
}

wchar_t ****myDB = NULL;

(dllexport)wchar_t ****GetDB()
{
	myDB = GetDataBase();
	return myDB;
}

(dllexport)void FreeMem()
{
    free(myDB);
}

(dllexport)void GetDB(wchar_t ****myDB)
{
    myDB = GetDataBase();
}

(dllexport)void FreeMem(void *addr)
{
    free(addr);
}
// oef c

// C# starts

IntPtr myDB = IntPtr.Zero; // pointer
GetDB(ref myDB);   //pivoke
// do stuff with myDB
FreeMem(myDB);    //pinvoke