c#捕获窗口最小化和还原的事件

[DllImport("user32.dll", EntryPoint = "SendMessage")]
        private static extern int SendMessage(IntPtr hWnd, int Msg, int wParam, int lParam);

        const int WM_SYSCOMMAND = 0x0112;
        const int SC_MINIMIZE = 0xF020;
        const int SC_MAXIMIZE = 0xF030;
        const int SC_RESTORE = 0xF120;

        protected override void WndProc(ref Message m)
        {
            base.WndProc(ref m);
            if (m.Msg==WM_SYSCOMMAND)
            {
                int sc = m.WParam.ToInt32();
                if (sc == SC_MINIMIZE || sc == SC_RESTORE)
                {
                    SendMessage(f2.Handle, m.Msg, sc, 0);
                }
            }
        }