Am I failing to include the necessary header files or allocate memory? What
data types - LPSTR/LPTSTR - Unicode or ANSI?

Could a VC++ expert point me at a simple DLL that illustrates string
manipulation.

Many thanks,

John Way

At the C++ end:

extern "C" long WINAPI StringOp(LPSTR lpszString, long nSize)
{
    CString        csTest = "Hello world";

    if (csTest.GetLength() <= nSize)
        strcpy(lpszString, (LPCSTR) csTest);

    return csTest.GetLength();

VB end:

declare function StringOp lib "MyDll.dll"(byval lpszString$, byval nSize&)
as long

VB usage:

    dim StrRet$
    dim nRet&

    StrRet$ = space$(100)
    nRet& = StringOp(StrRet$, len(StrRet$))
    if nRet& > len(StrRet$) then
        StrRet$ = space$(nRet&+1)
        nRet& = StringOp(StrRet$, len(StrRet$))
    end if
    StrRet$ = left$(StrRet$, nRet&)

Note that the string pointer is declared ByVal even though it is a pointer.
This is a language "feature" you just have to get used to <g>.  Apparently
it instructs VB to convert the BSTR (which is what VB stores strings as) to
a LPSTR.

BTW untested code, so I hope not too many typos!

HTH

Peter Beach

As Peter Beach points out, you have to pass the string ByVal although you
have a pointer as argument in your C or C++ function. Note that you can't
pass the content of a text-box directly (e.g ok=dosomething(txtText.Text)),
you have to copy it to a string first. I did some small stuff in that way
and it works fine. Seems that passing string-arrays is a far more hairy
thing (no advice for this, as I'm no expert...).