What is the best way to return an arbitrary sized array of 'strings' from a C++ originated .dll to a VB.NET application

See more:

C++

C#

VB

VC++

I will be writing several .dll's to act as loadable Parser's for user settable hardware devices (somewhat similar to plugins). The .DLL's will be selected and loaded at run time by the user.

Several of the functions within the .DLL will be required to return a series of strings such as a list of supported features... or group of accessible locations... etc...

The returned strings will be displayed in a ListBox or Combobox within a vb.net application (which i will also be writing)...


I have spent a considerable length of time searching online (google, forums etc) and although I am new to VB.net, I do have some experience with Pascal, Delphi, C, C++ and VB and I understand the mechanics of dynamically loading using the LoadLibrary, FreeLibrary, GetProcAddress, etc... But I am now getting totally confused and frustrated by the Marshalling, importing, exporting, SafeArray, COleSafeArray, etc


Am i going about this the right way, or is there a better way of doing what i am trying to achieve.

What I have tried:

// in Driver.h
__declspec(dllexport) SAFEARRAY* _stdcall DriverGetLOT();

// in Driver.cpp
void FillSafeArray(OLECHAR FAR *sz, int iRow, COleSafeArray *sa)
{
	VARIANT v;
	long index[1];
	index[0] = iRow;
	VariantInit(&v);
	v.vt = VT_BSTR;
	v.bstrVal = SysAllocString(sz);
	sa->PutElement(index, v.bstrVal);
	SysFreeString(v.bstrVal);
	VariantClear(&v);
}


SAFEARRAY* _stdcall DriverGetLOT()
{
	DWORD saBounds[] = {4};

	COleSafeArray saRet;

	saRet.Create(VT_BSTR, 1, saBounds);
	FillSafeArray(strBatchName.AllocSysString(),0,&saRet);
	FillSafeArray(strWaferName.AllocSysString(),1,&saRet);
	FillSafeArray(strExpectedYield.AllocSysString(),2,&saRet);
	FillSafeArray(strOperatorName.AllocSysString(),3,&saRet);
	return saRet.Detach(); // <=== gives a cant convert VARIANT to SAFEARRAY error
}

// in Vb.NET
Public Class myClass

Private Declare Function DriverGetLOT Lib "Driver.dll"() As string() ' also tried object and VARIANT here 


Sub DoStuff()
  Me.lbLOTinfo.Items.AddRange(DriverGetLOT())
end sub

end class