public bool AddCostumer(Costumer c)//adds a Costumer { if (!(int.Parse(c.tz) > 0 && (int.Parse(c.tz) < 1000000000))) { throw new Exception("costumer name numst be a string...try again please"); } if (c.costumerAge < 18) { throw new Exception("costumer age under 18...try again please"); } return(dal.AddCostumer(c)); }