private void btnAddClassType_Click(object sender, EventArgs e)
        {
            loai = 1; // them loai lớp
            Panel pnlManage = this.Parent as Panel;

            if (pnlManage != null)
            {
                UserControlClassManage classmanageControlUser = new UserControlClassManage();
                classmanageControlUser.getLoaiThamSo(loai, "", "", "", "");
                pnlManage.Controls.Clear();
                pnlManage.Controls.Add(classmanageControlUser);
                classmanageControlUser.Dock = DockStyle.Fill;
            }
        }
        private void btnAddClass_Click(object sender, EventArgs e)
        {
            loai = 3; // them lớp
            Panel  pnlManage  = this.Parent as Panel;
            string maloailop  = dtgClassType.CurrentRow.Cells["ID_ClassType"].Value.ToString();
            string tenloailop = dtgClassType.CurrentRow.Cells["ClassType_Name"].Value.ToString();

            if (pnlManage != null)
            {
                UserControlClassManage classmanageControlUser = new UserControlClassManage();
                classmanageControlUser.getLoaiThamSo(loai, maloailop, tenloailop, "", "");
                pnlManage.Controls.Clear();
                pnlManage.Controls.Add(classmanageControlUser);
                classmanageControlUser.Dock = DockStyle.Fill;
            }
        }
        private void btnEditClass_Click(object sender, EventArgs e) // xử lý sự kiện nút chỉnh sửa
        {
            loai = 4;                                               // loai 4 la chinh sua lop
            Panel  pnlManage  = this.Parent as Panel;
            string maloailop  = dtgClassType.CurrentRow.Cells["ID_ClassType"].Value.ToString();
            string tenloailop = dtgClassType.CurrentRow.Cells["ClassType_Name"].Value.ToString();
            string malop      = dtgvClass.CurrentRow.Cells["ID_Class"].Value.ToString();
            string tenlop     = dtgvClass.CurrentRow.Cells["Class_Name"].Value.ToString();

            if (pnlManage != null)
            {
                UserControlClassManage classmanageControlUser = new UserControlClassManage();
                classmanageControlUser.getLoaiThamSo(loai, maloailop, tenloailop, malop, tenlop);
                pnlManage.Controls.Clear();
                pnlManage.Controls.Add(classmanageControlUser);
                classmanageControlUser.Dock = DockStyle.Fill;
            }
        }