C++ DLL Returning a String to VB

[gameschild]

Created the following code in C++:

char* __stdcall getArrayFolderPath(int pos)
{
    return Folder[pos].Folder_Path;
}

And in Visual Basic declared the DLL as:

Public Declare Function getArrayFolderPath Lib "DirXCore.dll" (ByVal pos As Long) As String

However the string returned is empty. If i change "As String" to "As Byte" i get a number but it two digits, maybe a single char?

Anyone know how i can make the C++ DLL return the string to VB?

[K]

you will need to pass an empty string as a parameter and copy the c string into it. Something like:

Code Select Expand


int __stdcall getArrayFolderPath(char* lpszBuffer, int nBuffLen, int pos)
{
    int len = strlen(Folder[pos].Folder_Path);
    if (nBuffLen < len)
         return -1; // Error: not enough space in buffer
   
    strcpy(lpszBuffer, Folder[pos].Folder_Path);
   
    return len;
}


Although you might run into trouble since VB uses BSTRs.

Code Select Expand


Public Declare Sub getArrayFolderPath Lib "DirXCore.dll" (ByVal Buffer As String, ByVal BufferLength As Long, ByVal pos As Long) As Long

// I don't really know VB.
Dim myStr As String
Dim strLen as Long

myStr = Space(255)
strLen = getArrayFolderPath(myStr, 255, pos)
If strLen == -1 Then
  // More than 255 characters in string


[gameschild]

    Dim myStr As String
   Dim strLen As Long
   myStr = Space(255)
   strLen = getArrayFolderPath(myStr, 255, pos)
   List1.AddItem Left(myStr, strLen)
   If strLen = -1 Then
   msgbox "More than 255 Chars"

And it works brilliantly, thanks a lot!

[UserLoser.]

// I don't really know VB.

You really show it  VB uses ' or REM for comments

[K]

// I don't really know VB.

You really show it  VB uses ' or REM for comments

I know. I like // better. Same with the == in the If statement.  

[hismajesty]

// I don't really know VB.

You really show it  VB uses ' or REM for comments

I know. I like // better. Same with the == in the If statement.  

My friend does ' // for his VB comments.

[Skywing]

Have you tried using SysAllocString or SysAllocStringByteLen to allocate the string returned?  Perhaps one of those might work.