public sealed class CompanyDataManager
    {
        private static readonly CompanyDataManager instance = new CompanyDataManager();

        private CompanyDataManager()
        {
        }

        public static CompanyDataManager Instance
        {
            get { return instance; }
        }

        private static IList<string> _countries;
        private static IList<string> Countries
        {
            get
            {
                if (_countries == null)
                {
                    EntityCollection<CountryEntity> collection = CompanyInformationDAO.GetCountries();
                    _countries = collection.Select(c => c.Country).ToList();
                }
                return _countries;
            }
        }