//Sửa nhân viên
 public int updateKhachHang(KhachHangDTO khDTO)
 {
     try
     {
         var querry = (from kh in htDataContext.khachhangs
                       where kh.makhachhang == khDTO.Makhachhang
                       select kh).FirstOrDefault<khachhang>();
         querry.tenkhachhang = khDTO.Tenkhachhang;
         querry.gioitinh = (Boolean)khDTO.Gioitinh;
         querry.cmnd_passport = khDTO.CMND_PASSPORT;
         querry.diachi = khDTO.Diachi;
         querry.pass = khDTO.Pass;
         querry.sodienthoai = khDTO.Sodienthoai;
         querry.email = khDTO.Email;
         htDataContext.SubmitChanges();
         return 1;
     }
     catch
     {
         return 0;
     }
 }
 //Thêm nhân viên
 public int insertKhachHang(KhachHangDTO khDTO)
 {
     try
     {
         khachhang kh = new khachhang();
         kh.makhachhang = khDTO.Makhachhang;
         kh.tenkhachhang = khDTO.Tenkhachhang;
         kh.gioitinh = (Boolean)khDTO.Gioitinh;
         kh.cmnd_passport = khDTO.CMND_PASSPORT;
         kh.diachi = khDTO.Diachi;
         kh.pass = khDTO.Pass;
         kh.sodienthoai = khDTO.Sodienthoai;
         kh.email = khDTO.Email;
         htDataContext.khachhangs.InsertOnSubmit(kh);
         htDataContext.SubmitChanges();
         return 1;
     }
     catch
     {
         return 0;
     }
 }