The Winform program child form is embedded in the parent form

  #region 嵌入窗体显示
        private void CloseForm()
        {
            //遍历spContainer.Panel2中的控件，如果存夺Form控件，则将它关闭。
            foreach (Control item in this.spContainer.Panel2.Controls)
            {
                if (item is Form)//如果是Form控件，就将它关闭掉
                {
                    Form objControl = (Form)item;
                    objControl.Close();
                }
            }
        }
        private void OpenForm(Form objForm)
        {
            CloseForm();
            //嵌入的基本步骤
            objForm.TopLevel = false;//将子窗体设置成非顶级控件 
            objForm.FormBorderStyle = FormBorderStyle.None;//去掉窗体的边框
            objForm.Parent = this.spContainer.Panel2;//指定窗体显示的容器
            objForm.Dock = DockStyle.Fill;//设置子窗体随着容器大小自动调整窗体大小 
            objForm.Show();
        }

        //显示添加新学员窗体       
        private void tsmiAddStudent_Click(object sender, EventArgs e)
        {
            FrmAddStudent