datacontext

public class VivendaContext : DbContext
    {
        public DbSet<Premise> Premises { get; set; }
        public DbSet<Person> Persons { get; set; }
        public DbSet<PremiseType> PremiseTypes { get; set; }
        public DbSet<RentContract> RentContracts { get; set; }
        public DbSet<BuyContract> BuyContracts { get; set; }
        public DbSet<Property> Properties { get; set; }
        public DbSet<Address> Addresses { get; set; }
        public DbSet<Town> Towns { get; set; }
        public DbSet<Meter> Meters { get; set; }
        public DbSet<Counter> Counters { get; set; }
        public DbSet<CounterReading> CounterReadings { get; set; }

        private static VivendaContext _Current;

        public static VivendaContext Current
        {
            get
            {
                if (_Current == null)
                {
                    _Current = new VivendaContext();
                }
                return _Current;
            }
        }

        protected VivendaContext()
        {
            LoadTowns();
        }

        private void LoadTowns()
        {
            if (Towns.ToList().Count == 0)
            {
                var xml = XDocument.Load("DataModels/postalCodes.xml");
                var towns = from data in xml.Element("Codes").Elements("Code")
                            select new Town
                            {
                                Name = this.NormalizeName(data.Element("Row").Attribute("Name").Value),
                                PostalCode = data.Element("Row").Attribute("Code").Value
                            };

                foreach (var town in towns)
                {
                    Towns.Add(town);
                }
                this.SaveChanges();
            }
        }

        private string NormalizeName(string name)
        {
            if (name.ToUpper(CultureInfo.InvariantCulture) == name)
            {
                return name.First().ToString().ToUpper() + name.Substring(1).ToLower();
            }
            return name;
        }

        protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
            modelBuilder.Entity<Premise>().HasMany(p => p.Meters).WithRequired(m => m.Premise);

            modelBuilder.Entity<Meter>().HasMany(c => c.Counters)
            .WithRequired(r => r.Meter)
            .WillCascadeOnDelete();
            modelBuilder.Entity<Counter>().HasMany(c => c.Readings)
                .WithRequired(r => r.Counter)
                .WillCascadeOnDelete();
        }

        public bool IsAddressOccupied(Address address)
        {
            return
                this.Addresses.FirstOrDefault(
                    a =>
                        a.AddressId == address.AddressId
                        || a.Number == address.Number
                            && a.NumberExtension == a.NumberExtension
                            && a.Street == address.Street
                            && a.Town.Name == address.Town.Name
                            && a.Town.PostalCode == address.Town.PostalCode
                ) != null;
        }

        public static void Save()
        {
            Current.SaveChanges();
        }
    }