saleMain.Date = DateTime.Now;

context.SaveChanges();

protected override string Generate(DateTime defaultValue) {
            var value = defaultValue.Ticks != 0 ?
                defaultValue.ToString("yyyy-MM-dd HH:mm:ss", CultureInfo.InvariantCulture) :
                "1753-01-01 00:00:00";

            return string.Format("'{0}'", value);
        }