private void btnThem_Click(object sender, EventArgs e)
        {
            FormThem_CapNhatTacGia newForm = new FormThem_CapNhatTacGia();

            this.Visible = false;
            newForm.Show();
            newForm.Disposed += NewForm_Disposed;
        }
        private void btnSua_Click(object sender, EventArgs e)
        {
            DataGridViewRow row = dataGVTacGia.SelectedRows.Count >= 1 ? dataGVTacGia.SelectedRows[0] : null;

            if (row != null)
            {
                string maTacGia  = row.Cells["colMaTG"].Value.ToString();
                string tenTacGia = row.Cells["colTenTG"].Value.ToString();
                FormThem_CapNhatTacGia newForm = new FormThem_CapNhatTacGia(maTacGia, tenTacGia);
                this.Visible = false;
                newForm.Show();
                newForm.Disposed += NewForm_Disposed;
            }
            else
            {
                MessageBox.Show("Bạn chưa chọn tác giả để sửa");
            }
        }