public void InsertKH(KhachHang kh)
        {

            db.KhachHangs.Add(kh);
            db.SaveChanges();

        }
 public void UpdateDS(KhachHang kh)
 {
     KhachHang capnhat = this.db.KhachHangs.Single(s => s.MaKhachHang == kh.MaKhachHang);
     capnhat.MaKhachHang = kh.MaKhachHang;
     capnhat.TenKhachHang = kh.TenKhachHang;
     capnhat.CMND = kh.CMND;
     capnhat.NgaySinh = kh.NgaySinh;
     capnhat.Sdt = kh.Sdt;
     capnhat.QueQuan = kh.QueQuan;
     db.SaveChanges();
 }