Handle for ShellExecute() - Parent Window?

Question

I am trying to use ShellExecute to open a file in Excel. I was reading about the function on MSDN forums, and I found the folowing information about the handle, which is the first parameter:

"hwnd [in] A handle to the owner window used for displaying a user interface (UI) or error messages. This value can be NULL if the operation is not associated with a window."

I have also heard this referred to as the handle to the parent window. What is the parent/owner window? As you see below I am using NULL for the handle, but since the operation is indeed associated with a window, I probably need a handle, but I don't know what to use for the handle.

ShellExecute(NULL, "open" ,"Excel.exe", 
    "C:\\Documents and Settings\\Lab1\\My Documents\\Test.xls", 
    NULL, SW_SHOWNORMAL);

Just added quotes suggestions. Tell me if one of those combinations works. — VonC
did you try the double double quote properley ? It has actually three double quotes: " " " at the beginning and the end. — VonC
I tried with three double quotes, and it still says that it can't find the file. — Shishiree
If this path does exist (if you can make a 'dir' on it), what is left is to try every quote combinations you can think of ;) — VonC

VonC VonC · Accepted Answer · 2008-11-24T21:32:51

It is usually 0

hwnd : parent window that will receive a possible messagebox. This parameter is usually 0.

It refers to the top-level window: the window you are opening does not have any parent, and is the main window for the application being executed.

When you are switching between applications (ALT-TAB), you are displaying the next top-level window (the next app with a parent handle equals to 0) in the z-order (for instance).

Of course, the parent to your app can not be the Desktop Window itself:

If you create a child window whose parent is GetDesktopWindow(), your window is now glued to the desktop window. If your window then calls something like MessageBox(), well that's a modal dialog, and then the rules above kick in and the desktop gets disabled and the machine is toast.

For the path, I would advice double quotes surrounding simple quotes: " ' ... ' "

"'C:\\Documents and Settings\\Lab1\\My Documents\\Test.xls'"

Could work also (untested) with double double quotes : " "" ... "" "

"""C:\\Documents and Settings\\Lab1\\My Documents\\Test.xls"""

, as illustrated by this thread.

Actually, as mentioned in your other question by Andy and by Mesidin, and in ShellExecute Function manual, you can open the file, and pass its path in parameter.

ShellExecute( NULL, "open", 
              "Test.xls", "C:\\Documents and Settings\\Lab1\\My Documents\\", 
              NULL, SW_SHOWNORMAL);

That means Excel is the default application for opening .xls extension files though.

Handle for ShellExecute() - Parent Window?

4 Answers