public StreetAddress(string _street, int _houseNumber)
        {
            StreetAddress newAddress = new StreetAddress();

            addresses.Add(newAddress);
            newAddress.street      = _street;
            newAddress.houseNumber = _houseNumber;
        }
        public int CompareTo(object _other)
        {
            int           results = 0;
            StreetAddress other   = (StreetAddress)_other;

            if (this.street != other.street)
            {
                results = this.street.CompareTo(other.street);
            }
            else
            {
                results = this.houseNumber.CompareTo(other.houseNumber);
            }
            return(results);
        }