NHibernate IUserVersionType for MSSQL rowversion columns

RowVersionType.cs

    public class RowVersionType : IUserVersionType
    {
        public object Seed(ISessionImplementor session)
        {
            return 0ul;
        }

        public object Next(object current, ISessionImplementor session)
        {
            return current;
        }

        public new bool Equals(object x, object y)
        {
            return object.Equals(x, y);
        }

        public int GetHashCode(object x)
        {
            return x.GetHashCode();
        }


        public object NullSafeGet(IDataReader rs, string[] names, object owner)
        {
            byte[] value = (byte[]) NHibernateUtil.Binary.NullSafeGet(rs, names);
            if (value == null) return null;
            return unchecked((ulong) IPAddress.NetworkToHostOrder(BitConverter.ToInt64(value, 0)));
        }

        public void NullSafeSet(IDbCommand cmd, object value, int index)
        {
            if (value == null) NHibernateUtil.Binary.NullSafeSet(cmd, null, index);
            else
            {
                value = BitConverter.GetBytes(IPAddress.HostToNetworkOrder(unchecked((long) (ulong) value)));
                NHibernateUtil.Binary.NullSafeSet(cmd, value, index);
            }
        }


        public object DeepCopy(object value)
        {
            return value;
        }

        public object Replace(object original, object target, object owner)
        {
            return original;
        }

        public object Assemble(object cached, object owner)
        {
            return cached;
        }

        public object Disassemble(object value)
        {
            return value;
        }

        public SqlType[] SqlTypes
        {
            get
            {
                return new[] {new SqlType(DbType.Binary, 8)};
            }
        }

        public Type ReturnedType
        {
            get
            {
                return typeof (ulong);
            }
        }

        public bool IsMutable
        {
            get
            {
                return false;
            }
        }

        public int Compare(object x, object y)
        {
            ulong? a;
            ulong? b;

            a = x == null ? (ulong?) null : (ulong) x;
            b = y == null ? (ulong?) null : (ulong) y;
            
            return System.Collections.Generic.Comparer<ulong?>.Default.Compare(a, b);
        }
    }