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 example, on computer A, “text.txt” will be opened in wordpad but on computer B it will be opened by Notepad++ because of the users file extension assignments.

I tried ShellExecute

ShellExecute(0, L"open", L"c:\\windows\\notepad.exe" ,L"c:\\outfile.txt" , 0 , SW_SHOW );

which works but if I omit the notepad.exe parameter weird things happen (a random explorer is shown).

Answer 1

You want to use the file to open as the file argument, not the parameter argument. No need to specify which program to use, ShellExecute will look it up for you.

ShellExecute(0, 0, L"c:\\outfile.txt", 0, 0 , SW_SHOW );

By leaving the verb as NULL (0) rather than L"open", you get the true default action for the file type – usually this is open but not always.