public Sach()
{
MaSach = 0;
TenSach = "";
Loai = new LoaiSach(0);
TenTG = "";
NSB = "";
GiaTien = 0;
SoLuong = 0;
}
public Sach(int id)
{
MaSach = id;
DataTable dt = SachControl.layThongTin(id);
TenSach = dt.Rows[0]["TenSach"].ToString();
Loai = new LoaiSach(Convert.ToInt32(dt.Rows[0]["Loai"].ToString()));
TenTG = dt.Rows[0]["TenTG"].ToString();
NSB = dt.Rows[0]["NSB"].ToString();
GiaTien = double.Parse(dt.Rows[0]["GiaTien"].ToString());
SoLuong = Convert.ToInt32(dt.Rows[0]["SoLuong"].ToString());
}