using sendmessage to send wm_close to another process

Question

I want to send wm_close to another process, with which i want end that process safely.

int _tmain(int argc, _TCHAR* argv[])
{

    DWORD SetOfPID;
    SetOfPID = GetProcId(_T("abc.exe"));  //this will return pid
    HANDLE h = OpenProcess(PROCESS_ALL_ACCESS,false, SetOfPID);

    HWND hwnd = ::GetTopWindow(NULL);
    while(hwnd)
    {
        DWORD pid;
        DWORD dwThreadId = ::GetWindowThreadProcessId(hwnd, &pid);
         if(pid == SetOfPID)
         {    
              break;
         }
         hwnd = ::GetNextWindow(hwnd, GW_HWNDNEXT);
    }
    //DestroyWindow(hwnd);
    bool temp = IsWindow(hwnd); **//this gives true**
    LRESULT res = ::SendMessage(hwnd, WM_CLOSE, NULL, NULL);
    DWORD err = GetLastError(); **//this gives 6**
    CloseHandle(hwnd);
    CloseHandle(h);
    return 0;
}

this piece of code looks good, but the target process doesn't terminate, can somebody help me?

Solution 1

Are you sure that the window you are finding is the correct one? You can check easily with Spy++. Moreover, when searching for a window, I think it's better to use EnumWindows. I'm not sure your method is correct.

Solution 2

I would attempt to close a (Process with) Window(s) in the following order:

1. WM_CLOSE

2. WM_QUIT

3. WM_DESTROY

4. TerminateProcess().

Just my take as I am handling (disabling) WM_CLOSE for a Window and having difficulty distinguishing between User Close and close messages send by another master task. WM_QUIT seems to resolve my problem without using a custom WM_APP_CLOSE of my own. TerminateProcess is very much a last resort unclean exit to be avoided at all costs (it may leave handles (e.g. COM etc) and memory etc unfreed).

Comments

[rplusg]

WM_DESTROY and WM_NCDESTROY also doesn't work. DestroyWindow() also returns false.

[rplusg]

IsWindow() returns true, doesn't it mean i've a valid window?

[David Heffernan]

WM_DESTROY and WM_NCDESTROY can't work, they are notifications.

[pagra]

@rplusg: IsWindow tells you it is a valid window handle, not more. It can be that the application has got several top level windows, maybe not visible. And you may not close the right one.

[rplusg]

even i'm not sure what is the problem, but enumwindows has given my desired results. Thanks patriiice, marking your answer as final.