protected void WriteCreateXml(XmlTextWriter writer, RecurlyAccount account, string couponCode, int? billingCycles, DateTime? firstRenewalDate)
{
writer.WriteStartElement(ElementName); // Start: subscription
writer.WriteElementString(PlanCodeElement, PlanCode); //Required
account.WriteXml(writer); //Required
writer.WriteElementStringIfProvided(CouponCodeElement,couponCode);
writer.WriteElementIntIfProvided(UnitAmountInCentsElement, UnitAmountInCents);
writer.WriteElementString(CurrencyElement,Currency); //Required
writer.WriteElementIntIfProvided(QuantityElement, Quantity > 1 ? Quantity : new int?());
writer.WriteElementDateTimeIfProvided(TrialEndsAtElement, TrialEndsAt);
writer.WriteElementDateTimeIfFuture(StartsAtElement,ActivatedAt);
writer.WriteElementIntIfProvided(TotalBillingCyclesElement, billingCycles);
writer.WriteElementDateTimeIfProvided(FirstRenewalDateElement, firstRenewalDate);
writer.WriteElementListIfAny(AddonsElement, Addons, (w, a) => a.WriteXml(w));
WriteManualInvoiceElement(writer);
writer.WriteEndElement(); // End: subscription
}