How can you open a file with the program associated with its file extension?

Question

Is there a simple way to open a file by its associated program in windows? (like double clicking it in windows explorer but done automatically with my code)

For exam

Answer 1

A little more possibilities here:

If you want to open - for example - the file by default with Notepad++ (if installed), you could scan for it's registry key if it exists and where it is, (Usually HKLM\SOFTWARE\Wow6432Node\Notepad++ [tested Win7]) then take that path and open it.

std::wstring file = L"C:\\Outfile.txt";

if (NotepadPlusPlusExists()) //Open with Notepad++ or use an other program... (maybe your own ?)
{
    std::wstring wsNPPPath = GetNotepadPlusPlusPath();
    ShellExecuteW(HWND, L"open", wsNPPPath.c_str(), file.c_str(), NULL, SW_NORMAL);
}
else //Open with default associated program <---
    ShellExecuteW(HWND, NULL, file.c_str(), NULL, NULL, SW_NORMAL);

If you want the user to be able to change the default program or select a program he/she wants to use, you may open the "Open with" dialog.

//std::wstring StringArgsW(const wchar_t *format, ...);
std::wstring wsCmdOpenWith = StringArgsW(L"C:\\Windows\\system32\\shell32.dll,OpenAs_RunDLL \"%s\"", file.c_str());
ShellExecuteW(HWND, L"open", L"C:\\Windows\\system32\\rundll32.exe", wsCmdOpenWith.c_str(), NULL, SW_NORMAL);

You can also open the file in explorer.

std::wstring wsCmdExplorer = StringArgsW(L"/select,\"%s\"", file.c_str());
ShellExecuteW(HWND, L"open", L"explorer.exe", wsCmdExplorer.c_str(), NULL, SW_NORMAL);