How do I declare a string and pass it from a Visual Basic GUI to a C++ DLL?

How do I declare a string and pass it from a Visual Basic GUI to a C++ DLL?

Now I am debugging successfully. I can debug either on the Visual Basic end or I can debug on the C++ side by using the DLL's project file and declaring the compiled VB code as the launching executable. I have narrowed the problem down to the way that I am declaring and passiing the string variables.

Here is a sample to get user name via windows api function (basically the same thing you're after):

VB Code:

Private Declare Function GetUserName Lib "advapi32.dll" Alias "GetUserNameA" 
    (ByVal lpBuffer As String, nSize As Long) As Long
 
Private Sub Form_Load()
Dim strUserName As String
 
    'Create a buffer
    strUserName = String(100, Chr$(0))
    
    'Get the username
    GetUserName strUserName, 100
    
    'strip the rest of the buffer
    strUserName = Left$(strUserName, InStr(strUserName, Chr$(0)) - 1)
 
End Sub

an example,

VB Code:

#include <windows.h>
 
BOOL APIENTRY DllMain (HINSTANCE hInst, DWORD reason, LPVOID reserved){
    return TRUE;
}
 
extern "C" __declspec( dllexport ) __stdcall char *UChar(char *);
 
extern "C" __declspec( dllexport ) __stdcall char *UChar(char *UCaseString)
 
{
 
    int StrUCaseLen;
 
    StrUCaseLen=strlen(UCaseString);
 
    char *myChar = new char[StrUCaseLen+1];
 
    strncpy(myChar,UCaseString,StrUCaseLen);
 
    return strupr(myChar) ;
 
}

VB Code:

Private Declare Function UChar Lib "c:\dll.dll" (ByVal strTxt As String) As String
 
Private Sub Command1_Click()
 
    MsgBox UChar("huh¿")
 
End Sub

you don't need a def file if doing it this way..