private void btnXoa_Click(object sender, EventArgs e)
        {
            DialogResult result;

            result = MessageBox.Show("Bạn có chắc chắn muốn xóa không ?", "Hệ Thống", MessageBoxButtons.YesNo);
            if (result == DialogResult.Yes)
            {
                string sql = "MaNhomHP='" + txtMaNhomHP.Text + "'";
                business.Delete("NhomHocPhan", sql);
                FormNhomHocPhan_Load(sender, e);
            }
        }
        private void btnLuu_Click(object sender, EventArgs e)
        {
            string MaSV     = txtMaSV.Text;
            string MaNhomHP = cmbMaNhomHP.SelectedValue.ToString();
            double DiemThi  = Convert.ToDouble(txtDiemThi.Text);
            double DiemQT   = Convert.ToDouble(txtDiemQuaTrinh.Text);
            string sql      = "MaSV='" + MaSV + "'";

            business.Delete("KetQua", sql);
            sql = "'" + MaSV + "','" + MaNhomHP + "'," + DiemQT + "," + DiemThi + ",'','',''";
            business.Insert("KetQua", sql);
            btnLoc_Click(sender, e);
        }