Protection level in C# code .

public bool ThemSP(Product p)
       {
           return productDAL.ThemSP(p);
       }
       private bool KiemTraSP(int maSP)
       {
           return productDAL.KiemTraSP(maSP);
       }
       public bool SuaSP(Product p)
       {
           if (KiemTraSP(p.ProductID))
               return productDAL.SuaSP(p);
           else
               return false;
       }