EnumChildWindows doesn't find all child windows

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I'm using Interop Services, trying to find all child windows in a process that I run from within my app. The app being run is IE. It finds the first two (BrowserFrameGripperClass and Client Caption) and then simply quits.

Relevant code:

C#

public static class WinAPI
{
    public delegate bool WindowEnumProc(IntPtr hwnd, IntPtr lparam);

    [DllImport("user32.dll")]
    [return: MarshalAs(UnmanagedType.Bool)]
    public static extern bool EnumChildWindows(IntPtr hwnd, WindowEnumProc callback, IntPtr lParam);
}

class public MyClass
{
    public IntPtr HWnd { get; set; }
    public List<IntPtr> Children { get; set; }
 
    public MyClass(IntPtr hwnd)
    {
    }

    public void RefreshChildren()
    {
        if (this.Children == null)
        {
            this.Children = new List<WindowHandle>();
        }
        else
        {
            this.Children.Clear();
        }
        if (this.HWnd != IntPtr.Zero)
        {
            List<IntPtr> childHandles = new List<IntPtr>();
            GCHandle gch = GCHandle.Alloc(childHandles);
            try
            {
                WinAPI.WindowEnumProc childProc = new WinAPI.WindowEnumProc(EnumerateChildWindow);
                WinAPI.EnumChildWindows(this.HWnd, childProc, GCHandle.ToIntPtr(gch));
                List<IntPtr> list = gch.Target as List<IntPtr>;
                foreach (IntPtr child in list)
                {
                    Children.Add(new WindowHandle(child));
                }
            }
            finally
            {
                if (gch.IsAllocated)
                {
                    gch.Free();
                }
            }
        }
    }

    public bool EnumerateChildWindow(IntPtr hwnd, IntPtr lParam)
    {
        bool result = true;
        GCHandle gch = GCHandle.FromIntPtr(lParam);
        List<IntPtr> list = gch.Target as List<IntPtr>;
        result = (list.Count == 0);
        if (list != null)
        {
            list.Add(hwnd);
        }
        return result;
    }

}

Posted 9-Sep-14 4:21am

#realJSOP

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Comments

#realJSOP 9-Sep-14 10:31am

If you're not going to answer the question, STFU.

[no name] 9-Sep-14 10:41am

It's a troll John. Don't bother.

[no name] 9-Sep-14 14:09pm

hahaha

George Jonsson 9-Sep-14 10:32am

Rather ask every child about their children.
And do it recursively with the end state "children == null"

#realJSOP 9-Sep-14 10:55am

EnumChildWindows is *supposed* to enumerate all child windows and their children - if you recurse, you'll get all the windows more than once. My problem is that it's not even getting all of the main IE window's child windows. I don't know if this has anything to do with it, but it only found child windows that don't have their own child windows. These child windows are also the first two I see with Spy++.

If you open IE and then inspect the window with Spy++, you'll see what I mean.

George Jonsson 9-Sep-14 11:32am

I get your point. It was a very long time since I used this method and at that time I did the code in C++.
Trying to find some code sample now.

2 solutions

Solution 4

I changed the logic in

C#

public bool EnumerateChildWindow(IntPtr hwnd, IntPtr lParam)
{
    bool result = false ;
    GCHandle gch = GCHandle.FromIntPtr(lParam);
    List<IntPtr> list = gch.Target as List<IntPtr>;
    if (list != null)
    {
        list.Add(hwnd);
        result = true; // return true as long as children are found
    }
    return result;
}

The result is list of children, some with names and some without.

1 -
2 - Navigation Bar
3 -
4 -
5 -
6 -
7 -
8 -
9 - Address Combo Control
10 - Page Control
11 -
12 -
13 - SeConnect
14 -
15 - Search Combo Control
16 - Search Control
17 -
18 -
19 -
20 - Command Bar
21 -
22 -
23 -
24 - Favorites Command Bar
25 - LinksBand
26 - Favorites Bar
27 - Add to Favorites Bar
28 -
29 - ITBarHost
30 - Menu Bar
31 -
32 -
33 - Bing - Windows Internet Explorer provided by ...
34 -
35 -
36 - Zoom Level
37 -
38 -
39 -

I run the code from a console application and get the handle to the IE8 window via GetWindow.
Not sure if that has any significance.

Posted 9-Sep-14 6:34am

George Jonsson

Updated 9-Sep-14 6:37am

v2

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johannesnestler · Accepted Answer · 2014-09-09T05:15:00

Hi John,

Just a quick message - no solution I fear... Just want to tell you what I found out (or not)...

The documentation for EnumerateChildWindow states:

Enumerates the child windows that belong to the specified parent window by passing the handle to each child window, in turn, to an application-defined callback function. EnumChildWindows continues until the last child window is enumerated or the callback function returns FALSE

I suspect one (!) error is in the condition.

C#

result = (list.Count == 0)

If I try your code without this condition to enumerate VisualStudio's child windows I get ~10 but with your condition only 2... On iexplore it doesn't work at all on my system - the callback seems to be never called... ??? Sorry I didn't find the time to find out what may be the problem on my system. (I also tested with the original code found at )[^] - same results - not any childwindow for iexplore is found...

Anyway I can't spot any mistake in your code (except the above condition which is I think just an "additional" error).

Kind regards

Johannes