程序代码：

protected override void OnSizeChanged(EventArgs e)
        {
            SendMessage(this.Handle, 11, (IntPtr)0, (IntPtr)0);
            base.OnSizeChanged(e);

            if (VScroll) {
                this.ResetGroupWidth(-21);
            }
            else {
                this.ResetGroupWidth(-4);
            }
            this.HScroll = false;
            SendMessage(this.Handle, 11, (IntPtr)1, (IntPtr)0);
            this.Refresh();
        }

[DllImport("user32.dll", EntryPoint = "SendMessageA")]
        public static extern int SendMessage(IntPtr hwnd, int wMsg, IntPtr wParam, IntPtr lParam);