CODEWITHSUNDEEP
c#wpfwinapipinvoke
Nickersoft
Nickersoft

Reputation: 684

Why won't GetMenuItemInfo work?

I'm trying to read the label names of menu items in an active application and store them in a List<String>.

Unfortunately, dwTypeData ALWAYS returns null. Why is this?

            List<string> ls = new List<string>();
        IntPtr hMenu = Win32.GetMenu(hWnd);

            if (hMenu.ToInt32() != 0)
            {

                for (int i = Win32.GetMenuItemCount(hMenu); i >= 0; i--)
                {
                    try
                    {
                        uint MIIM_STRING = 0x00000040;
                        uint MFT_STRING = 0x00000000;
                        uint MIIM_TYPE = 0x00000010;
                        Win32.MENUITEMINFO mif = new Win32.MENUITEMINFO();
                        mif.cbSize = (uint)Marshal.SizeOf(typeof(Win32.MENUITEMINFO));
                        mif.fMask = MIIM_TYPE;
                        mif.fType = MFT_STRING;
                        mif.cch = 256;
                        mif.dwTypeData = "";
                        Win32.GetMenuItemInfo(hMenu, (uint)i, true, ref mif); //To load cch into memory
                        Win32.GetMenuItemInfo(hMenu, (uint)i, true, ref mif); //To fill dwTypeData
                        ls.Add(mif.dwTypeData);
                    }
                    catch { }

                }
            }

        return ls;

Upvotes: 0

Views: 1905

Answers (3)

J. F. De Rek ZA
J. F. De Rek ZA

Reputation: 11

Try to replace

mif.fMask = MIIM_TYPE;
mif.fType = MFT_STRING;

with

mif.fMask = MIIM_FTYPE;
mif.fType = MIIM_STRING;

The Win32 API MENUITEMINFOA documentation states that

MFT_STRING is replaced by MIIM_STRING.

Upvotes: 1

David Heffernan
David Heffernan

Reputation: 612993

Your problem is that you are trying to perform this action in a different process. When you call GetMenuItemInfo you pass the address of a MENUITEMINFO struct. But that address is only valid in your process. Because each process has its own private virtual memory space, that pointer that you send has no meaning in the other process.

It's possible that you could use VirtualAllocEx, WriteProcessMemory and ReadProcessMemory to allocate, write and read an instance of the MENUITEMINFO struct in the address space of the other process. That's your only hope of making this mechanism work. There are lots of examples to be found using websearch that illustrate the technique.

However, I would not recommend that you do that. You should use one of the standard automation interfaces to solve your actual problem. For example UIAutomation.

Upvotes: 1

Edward Clements
Edward Clements

Reputation: 5132

a) the loop should be for (int i = Win32.GetMenuItemCount(hMenu) - 1; i >= 0; i--)

b) before the first call to GetMenuItemInfo(), you need to set mif.dwTypeData to NULL (zero)

c) before the second call to GetMenuItemInfo(), mif.dwTypeData should point to a buffer allocated with a size of mif.cch + 1 -- see MSDN documentation

Make sure you deallocate the memory afterwards!

Upvotes: 1

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