private void btnInsertInputPoint_Click(object sender, EventArgs e) // quay trở lại user control insert point
        {
            Panel pnlManage = this.Parent as Panel;

            if (pnlManage != null)
            {
                UserControlStudent studentControl = new UserControlStudent(); // tạo usercontrol
                pnlManage.Controls.Clear();
                pnlManage.Controls.Add(studentControl);
                studentControl.Dock = DockStyle.Fill;
            }
        }
        private void btnStudent_Click(object sender, EventArgs e) // khi nhấn nút học viên load usercontrol Student ra quản lý
        {
            btnRegister.BackColor = SystemColors.ControlLightLight;
            btnStudent.BackColor  = SystemColors.ControlLight;
            btnClass.BackColor    = SystemColors.ControlLightLight;
            btnProcess.BackColor  = SystemColors.ControlLightLight;
            btnExam.BackColor     = SystemColors.ControlLightLight;
            btnSettings.BackColor = SystemColors.ControlLightLight;
            UserControlStudent studentControl = new UserControlStudent(); // tạo usercontrol

            pnlManage.Controls.Clear();
            pnlManage.Controls.Add(studentControl);
            studentControl.Dock = DockStyle.Fill;
        }