Question

How can I programatically find the handle of a user control in a webpage running on IE?

I’m able to find it using Spy++ but since the handle keeps changing I’m stuck.

I’ve been trying using FindWindow() but no luck 🙁 I also wonder if I am doing something wrong or it simply only work for Windows…

Thanks in advance,

Zubrowka

Answer 1

I had a similar problem finding a PDF ActiveX Control inside a IE control in WPF.

To overcome the problem I used the EnumChildWindows API to find the correct child window and thus get its handle.

I’ll include as much code as I can.

private static IntPtr FindPdfControlWindow(IntPtr parentHandle)
{
    IntPtr result = IntPtr.Zero;
    IntPtr matchPointer = IntPtr.Zero;
    try
    {
        //allocate unmanaged memory for the result of the callback delegate
        matchPointer = Marshal.AllocHGlobal(Marshal.SizeOf(typeof(IntPtr)));
        Marshal.WriteIntPtr(matchPointer, IntPtr.Zero)

        //instantiate the delegate and pass to the API
        NativeMethods.EnumWindowProc windowChecker = CheckForPdfControlWindow;
        if (!NativeMethods.EnumChildWindows(parentHandle, 
                                                windowChecker, 
                                                matchPointer))
    }
    finally
    {
        if (matchPointer != IntPtr.Zero) Marshal.FreeHGlobal(matchPointer);
    }
    return result;
}

private static bool CheckForPdfControlWindow(IntPtr handle,
                                                IntPtr matchPointer)
{
    int captionLength = NativeMehtods.GetWindowTextLength(handle);
    if (captionLength > 0)
    {
        StringBuilder buffer = new StringBuilder(captionLength + 1);
        NativeMethods.GetWindowText(handle, buffer, buffer.Capacity);
        if (buffer.ToString().Contains("Adobe"))
        {
            Marhsal.WriteIntPtr(matchPointer, handle)
            return false;
        }
    }
    return true;
}

private static class NativeMethods
{
    [DllImport("user32.dll")]
    [return: MarshalAs(UnmanagedType.Bool)]
    internal static extern bool EnumChildWindows(IntPtr window,
                                                    EnumWindowProc callback,
                                                    IntPtr i);

    internal delegate bool EnumWindowProc(IntPtr hWnd, IntPtr parameter);

    [DllImport("user32.dll", SetLastError = true, CharSet = CharSer.Auto)]
    internal static extern int GetWindowTextLength(IntPtr hWnd);

    [DllImport("user32.dll", SetLastError = true, CharSet = CharSet.Auto)]
    internal static extern int GetWindowText(IntPtr hWnd,
                                               StringBuilder lpString,
                                               int nMaxCount);
}

transcribed in a rush so I hope it is both helpful and accurate.