Find child window by class

Question

I can't get the "Edit" field handle when selecting a photo in a third-party application.

Spy++ shows everything correctly, but FindWindow fails. I can get the handle of the window itself, the parent. I assume I need to look for child windows. I can get some handles with GetWindow but but it's not clear what they are. The window title is empty. FindWindowEx doesn't work at all, returns 0. I indicate it like this:

IntPtr hwndchild = (hwnd, IntPtr.Zero, null, "Edit")

You are probably looking for [EnumChildWindows](https://learn.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-enumchildwindows). — 500 - Internal Server Error, Aug 22 '19 at 13:02
If that invalid line of C# code is supposed to represent the parameters to `FindWindowEx`, then the class is the third parameter, not the fourth. — GSerg, Aug 22 '19 at 13:07
[FindWindow](https://learn.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-findwindowa) - *Retrieves a handle to the **top-level** window*.. you have to enumerate children to get lower-level window as on screenshot. — Sinatr, Aug 22 '19 at 13:16
@500-InternalServerError Ok, i know, but how get child-handle by class? — Микка, Aug 22 '19 at 13:46
Call [GetClassName](https://learn.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-getclassname) for each handle returned, and compare with what you are looking for. Note that there'll typically be multiple child windows of the same class. — 500 - Internal Server Error, Aug 22 '19 at 13:49

Remy Lebeau · Answer 1 · 2019-08-22T18:03:45.123

Based on the screenshot you provided, and using just the FindWindow/Ex() functions, you can get the HWND of the Edit control like this:

IntPtr hwndDlg = FindWindow(null, "Choose an image");
IntPtr hwndCBEx = FindWindowEx(hwndDlg, IntPtr.Zero, "ComboBoxEx32", null);
IntPtr hwndCB = FindWindowEx(hwndCBEx, IntPtr.Zero, "ComboBox", null);
IntPtr hwndEdit = FindWindowEx(hwndCB, IntPtr.Zero, "Edit", null);

However, once you have the HWND to the ComboBoxEx control, the correct way to get the HWND of its Edit control is to use the CBEM_GETEDITCONTROL message:

const int CBEM_GETEDITCONTROL = 1031;
IntPtr hwndDlg = FindWindow(null, "Choose an image");
IntPtr hwndCBEx = FindWindowEx(hwndDlg, IntPtr.Zero, "ComboBoxEx32", null);
IntPtr hwndEdit = SendMessage(hwndCBEx, CBEM_GETEDITCONTROL, 0, 0);

Note, for a standard ComboBox control (which you can get from a ComboBoxEx control using the CBEM_GETCOMBOCONTROL message), you can use the CB_GETCOMBOBOXINFO message or the GetComboBoxInfo() function. The HWND of the Edit control is returned in the COMBOBOXINFO.hwndItem field.

Thank you, the best simple solution – Микка Aug 22 '19 at 17:45 — Микка, Aug 22 '19 at 17:45

score 0 · Answer 2 · answered Aug 22 '19 at 16:36

If you are looking for a child window of a parent you should use EnumChildWindows. The following is C++ code but could be pinvoked easily: you can marshal delegates as function pointers for the callback.

std::vector<HWND> FindChildrenByClass(HWND parent, const std::string& target_class)
{
    struct EnumWndParam {
        std::vector<HWND> output;
        std::string target;
    } enum_param;

    enum_param.target = target_class;

    EnumChildWindows(
        parent,
        [](HWND wnd, LPARAM lparam) -> BOOL {
            auto param = reinterpret_cast<EnumWndParam*>(lparam);
            char class_name[512];
            GetClassName(wnd, class_name, 512);
            if (param->target == class_name)
                param->output.push_back(wnd);
            return TRUE;
        },
        reinterpret_cast<LPARAM>(&enum_param)
    );

    return enum_param.output;
}

int main()
{
    auto windows = FindChildrenByClass( reinterpret_cast<HWND>(0x0061024A), "Edit");
    for (auto wnd : windows) {
        std::cout << std::hex << wnd << std::endl;
    }
}

Note in the above that I do not recursively call FindChildrenByClass in the callback lambda. This is not a mistake. EnumChildWindows already performs this recursion. It runs over a parent window's children and grand children, etc., out of the box without you having to specify this behavior or implement it.

score -5 · Answer 3 · answered Aug 22 '19 at 13:10

-5

Like someone already assumed. Try the EnumChildWindow method. Here is an complete sample already on stackoverflow

answered Aug 22 '19 at 13:10

Kinimod

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Find child window by class

3 Answers3