private void btnSearch_Click(object sender, EventArgs e)
        {
            eSinhVien sv = new eSinhVien();

            sv = svBLL.GetSinhVienByID(txtID.Text.Trim());
            if (sv != null)
            {
                txtTen.Text     = sv.HoVaTen;
                txtAddress.Text = sv.DiaChi;
                txtMail.Text    = sv.Mail;
                txtPhone.Text   = sv.SDT;
                txtLopNC.Text   = new LopNienCheBLL().GetLopNienCheByID(sv.ID_LopNienChe).TenLop.Trim();
                if (sv.HinhAnh != null)
                {
                    picHinhAnh.Image = ByteToImg(Convert.ToBase64String(sv.HinhAnh));
                }
                frmDangKyHocPhanPN frm = new frmDangKyHocPhanPN(sv);
                frm.TopLevel        = false;
                frm.Visible         = true;
                frm.FormBorderStyle = FormBorderStyle.None;
                frm.Dock            = DockStyle.Fill;


                panel.Controls.Clear();
                panel.Controls.Add(frm);
            }
            else
            {
                MessageBox.Show("Sai mã số sinh viên");
            }
        }
        public frmDangKyHocPhan(object tk)
        {
            InitializeComponent();
            this.taiKhoan = tk;
            if (tk is eSinhVien)
            {
                btnSearch.Visible = false;
                txtID.ReadOnly    = true;
                frmDangKyHocPhanPN frm = new frmDangKyHocPhanPN((eSinhVien)tk);
                frm.TopLevel        = false;
                frm.Visible         = true;
                frm.FormBorderStyle = FormBorderStyle.None;
                frm.Dock            = DockStyle.Fill;
                panel.Controls.Clear();
                panel.Controls.Add(frm);

                eSinhVien sv = (eSinhVien)tk;
                txtID.Text      = sv.ID_SinhVien;
                txtTen.Text     = sv.HoVaTen;
                txtAddress.Text = sv.DiaChi;
                txtMail.Text    = sv.Mail;
                txtPhone.Text   = sv.SDT;
                txtLopNC.Text   = new LopNienCheBLL().GetLopNienCheByID(sv.ID_LopNienChe).TenLop.Trim();
                if (sv.HinhAnh != null)
                {
                    picHinhAnh.Image = ByteToImg(Convert.ToBase64String(sv.HinhAnh));
                }
            }
            else
            {
                btnSearch.Visible = true;
                txtID.ReadOnly    = false;
            }
        }