Pass unicode string from VB.net to C++ dll

Question

I have tried a lot of things but I cannot get this to work. I can pass and receive ordinary strings (char*) to C++, but I cannot receive Unicode strings (w_char_t *) in C++.

Here are some bits of the code on c++

__declspec(dllimport) int __stdcall readFile(const w_char_t *file_path)

on VB.net

Public Declare Function readFile Lib "MyDll.dll" Alias "_readFile@4" (ByVal file_path As String) As Integer

when I change w_char_t to char I receive the correct string.

I have found a lot of material on VB6, but not for VB.net

Any help greatly appreciated.

Leon

Answer 1

Public Declare Unicode Function readFile Lib "MyDll.dll" Alias "_readFile@4" (ByVal file_path As String) As Integer

Also, your C++ code has dllexport not dllimport, right?

Answer 2

Try converting UnicodeString to String (by using some System Defined Function), and then pass that string or char* to C++ DLL.

Hope this will work.