Windows Forms: How to make mouse wheel event on the child controls scroll the parent panel

MousewheelControl.md

Make the form implement IMessageFilter and implement it as follows:

public bool PreFilterMessage(ref Message m)
{
    if (m.Msg == 0x20a)
    {
        // WM_MOUSEWHEEL, find the control at screen position m.LParam
        Point pos = new Point(m.LParam.ToInt32() & 0xffff, m.LParam.ToInt32() >> 16);
        IntPtr hWnd = WindowFromPoint(pos);
        if (hWnd != IntPtr.Zero && hWnd != m.HWnd)
        {
            var ctrl = Control.FromHandle(hWnd);
            if (ctrl.IsDescendentOf(theParentPanel))
            {
                SendMessage(theParentPanel.Handle, m.Msg, m.WParam, m.LParam);
                return true;
            }
        }
    }
    return false;
}

[DllImport("user32.dll")]
private static extern IntPtr WindowFromPoint(Point pt);
[DllImport("user32.dll")]
private static extern IntPtr SendMessage(IntPtr hWnd, int msg, IntPtr wp, IntPtr lp);

The above code assumes that the name of the parent panel is theParentPanel.

IsDescendentOf is an extension method that checks whether a control is a descendent of the provided container control:

public static bool IsDescendentOf(this Control ctrl, Control parent)
{
    while (true)
    {
        if (ctrl == null || ctrl.Parent == null)
            return false;

        if (ReferenceEquals(ctrl.Parent, parent))
            return true;

        ctrl = ctrl.Parent;
    }
}

In the end register this message filter (i.e., the form itself) in the form's constructor:

private MyForm()
{
    InitializeComponent();

    if(!DesignMode) // VS Designer may have problems with this
        Application.AddMessageFilter(this);
}

This solution is based on this forum thread.