MDI下隐藏父窗口滚动条

private const int SB_BOTH = 3;
        private const int WM_NCCALCSIZE = 0x83;

        [DllImport("user32.dll")]
        private static extern int ShowScrollBar(IntPtr hWnd, int wBar, int bShow);
        protected override void WndProc(ref Message m)
        {
            if (mdiClient != null)
            {
                ShowScrollBar(mdiClient.Handle, SB_BOTH, 0 /*Hide the ScrollBars*/);
            }
            base.WndProc(ref m);
        }
        MdiClient mdiClient = null;

        TTWorkPlan ttWorkPlan = new TTWorkPlan();　　　　　　//子窗口
        TTWorkRecord ttWorkRecord = new TTWorkRecord();　　//子窗口

        public TTWorkManagementSystem()
        {
            InitializeComponent();
        }

        private void TTWorkManagementSystem_Load(object sender, EventArgs e)
        {
            foreach (Control c in this.Controls) //Find the MdiClient in the MdiWindow  
            {
                if (c is MdiClient)
                {
                    mdiClient = c as MdiClient;
                }
            }

            ttWorkPlan.MdiParent = this;　　//设置子窗口父窗口
            ttWorkRecord.MdiParent = this;　　//设置子窗口父窗口

　　　　ttWorkRecord.Hide();　　//隐藏子窗口
            ttWorkPlan.Show();　　//显示子窗口
        }