Openfiledialog code working on VS2013 but failing in VS2019

Question

I have a C++ code I did on VS2005, it worked just fine and after a while I upgraded the project to VS2013 without issues, everything compiled and worked as expected.

Recently I upgraded one of my computers to VS2019 and tried to check one of my old programs there, the code didn't compile and threw me a bunch of errors related to conversion from const char* to LPCWSTR.

Function Call:

    std::string inputFile, cwd;
    cwd = getCWD();

    flag = openMultipleFileDialog("Select a valid CSV file.", "CSV Files (*.csv)\0*.csv\0\0", cwd, inputFile);

Function definition:

int openMultipleFileDialog(std::string title, char* filter, std::string cwd, std::string& fileName)
{
    int ofnFlag;
    char buffer[4096];
    OPENFILENAME ofn = {0};

    ofn.lStructSize = sizeof(ofn);
    ofn.lpstrFilter = filter;
    ofn.lpstrFile = buffer;
    ofn.lpstrFile[0] = '\0';
    ofn.nMaxFile = sizeof(buffer);
    ofn.lpstrTitle = title.c_str();
    ofn.lpstrInitialDir = cwd.c_str();
    ofn.Flags = OFN_PATHMUSTEXIST | OFN_FILEMUSTEXIST | OFN_EXPLORER;
    //ofn.Flags = OFN_PATHMUSTEXIST | OFN_FILEMUSTEXIST | OFN_EXPLORER | OFN_ALLOWMULTISELECT;

    ofnFlag = GetOpenFileName(&ofn);
    fileName = buffer;

    return ofnFlag;
}

I will update the post to add the VS2019 errors

I would like to know why is this happening, maybe something is flying under my radar and the VS upgrade came with a lot more changes than I expected.

Answer 1

Use the ASCII variants OPENFILENAMEA and GetOpenFileNameA instead of the non-explicit ones.

Search for information on Unicode support and the UNICODE macro for more information.

Answer 2

GetOpenFileName is declared as follows:

WINCOMMDLGAPI BOOL APIENTRY GetOpenFileNameA(LPOPENFILENAMEA);
WINCOMMDLGAPI BOOL APIENTRY GetOpenFileNameW(LPOPENFILENAMEW);
#ifdef UNICODE
#define GetOpenFileName GetOpenFileNameW
#else
#define GetOpenFileName GetOpenFileNameA
#endif // !UNICODE

GetOpenFileNameA, which takes a file path of type const char*.

GetOpenFileNameW, which takes a file path of type const wchar_t*.

However, the default Character Set of VS2019 is Unicode. So, it's calling the w version of the function. There's no automatic conversion from const wchar_t* to const char*. Therefore, I suggest that you could call GetOpenFileNameA explicitly instead of GetOpenFileName.