How to abort shutdown in Windows Vista and 7 programatically?

Question

In the second example (in the section examples) on this link, there is a description on using WM_QUERYENDSESSION to abort a shutdown. It also states that this does not work on versions of windows later than XP. This is conflicting with the advice given on another question here at stackoverflow. What is the correct answer? I do not have a computer with either so I am unable to test.

Answer 1

If anything else fails, remember that from command line it is shutdown.exe -a; maybe you could invoke this using the Process class.

EDIT. When mentioning the Process class I happily assumed that the question was about .NET programming, now I see that .NET is not mentioned neither in the question nor in the tags. Anyway I believe that there are ways to run executables from other programming environments as well.

Answer 2

Some applications got the WM_QUERYENDSESSION handling wrong (Not passing to DefWindowProc, they incorrectly returned 0 even though they did not intend to block shutdown) and so MS changed it with Vista, you now need to call ShutdownBlockReasonCreate()

@Konamiman: shutdown.exe -a will abort a "scheduled" shutdown yes, but not a "normal" shutdown by someone calling ExitWindowsEx()