null terminated character is not recognized - c++

Question

I use the OPENFILENAME ofn way to open a browse file dialog in win32 application.
I want to be able to use dynamic the file filtering according to what user needs and not as predefined to all files
ofn.lpstrFilter = L"All Files\0*.*\0\0";
I tried to change the predefined code with a dynamic one but it seems that even the null-terminated character is treated as string in the below code
string UserChoice = "Exe Files\0*.exe\0\0";
wstring ChoiceTemp = s2ws(UserChoice); // convert string to lpcwstr
LPCWSTR FilterByUser = ChoiceTemp.c_str();
ofn.lpstrFilter = FilterByUser;
It seems that the \0 is not recognized as null character in the browse file dialog and it doesn't show any files at all, my knowledge on c++ is on my first steps and i can`t make it work without any help on this issue and i searched around the net but nothing came in handy.
Any suggestion on how to make it work ?

Answer 1

You can use std::string for strings with embedded terminators, but you have to use the correct std::string constructor to create the string.
More specifically either the one where you explicitly specify a length (number 4 in the linked constructor reference) or a start and end iterator (number 6). In this case, the first one is best:
string UserChoice("Exe Files\0*.exe\0", 16);

Answer 2

lpstrFilter is usually a constant string so there is no need for std::wstring. Just define a constant string:
const wchar_t* filter =
L"All files\0*.*\0"
L"Exe files\0*.exe\0";
But it can be done as follows if necessary (I am repeating #Joachim Pileborg)
std::wstring filter =
L"All files|*.*|"
L"Exe files|*.exe|";
std::replace(filter.begin(), filter.end(), '|', '\0');
ofn.lpstrFilter = filter.data();
Use filter.data() instead of c_str(). To select a particular filter use nFilterIndex
wchar_t filename[MAX_PATH];
wcscpy_s(filename, L"c:\\test\\default file.txt");
OPENFILENAME ofn = { sizeof(OPENFILENAME) };
ofn.lpstrFile = filename;
ofn.nMaxFile = MAX_PATH;
ofn.lpstrFilter = filter;
ofn.nFilterIndex = 2; //select "Exe files"
ofn.Flags = OFN_PATHMUSTEXIST | OFN_FILEMUSTEXIST;