Line item calculator

7 min

extendedPrice

Calculates the price including the order-level discount amount (spread over all line items in the shipment) and any line item discount amount.

public void GetExtendedPrice(ILineItem lineItem, Currency currency, ILineItemCalculator lineItemCalculator) {
  var extendedPrice = lineItemCalculator.GetExtendedPrice(lineItem, currency);
  Debug.WriteLine("Extended price for '{0}': {1}", lineItem.Code, extendedPrice);
}

discountedPrice

Calculates the price with only the line item discount amount — that is, the discount for a specific line item.

public void GetDiscountedPrice(ILineItem lineItem, Currency currency, ILineItemCalculator lineItemCalculator) {
  var discountedPrice = lineItemCalculator.GetDiscountedPrice(lineItem, currency);
  Debug.WriteLine("Discounted price for '{0}': {1}", lineItem.Code, discountedPrice);
}

lineItemPrices

Calculates the line item prices — both the extended price and the discounted price for the line item.

public void GetLineItemPrices(ILineItem lineItem, Currency currency, ILineItemCalculator lineItemCalculator) {
  var lineItemPrices = lineItemCalculator.GetLineItemPrices(lineItem, currency);
  Debug.WriteLine("Extended price for '{0}': {1}", lineItem.Code, lineItemPrices.ExtendedPrice);
  Debug.WriteLine("Discounted price for '{0}': {1}", lineItem.Code, lineItemPrices.DiscountedPrice);
}

salesTax

The GetSalesTax method has two overloads — one for a single line item and one for a collection.

For a single line item:

public void GetSalesTax(ILineItem lineItem, IMarket market, Currency currency, IOrderAddress shippingAddress, ILineItemCalculator lineItemCalculator) {
  var salesTax = lineItemCalculator.GetSalesTax(lineItem, market, currency, shippingAddress);
  Debug.WriteLine("Sales tax for '{0}': {1}", lineItem.Code, salesTax);
}

For a collection of line items:

public Money GetSalesTax(IEnumerable<ILineItem> lineItems, IMarket market, Currency currency, IOrderAddress shippingAddress, ILineItemCalculator lineItemCalculator) {
  return lineItemCalculator.GetSalesTax(lineItems, market, currency, shippingAddress);
}

Change the default calculation

Inherit from DefaultLineItemCalculator, the default implementation of ILineItemCalculator, to override the extended price and sales tax calculations. To change the calculation of a line item's extended price, override the CalculateExtendedPrice method. To change the calculation of a line item's sales tax, override the CalculateSalesTax method.

public class LineItemCalculatorSample: DefaultLineItemCalculator {
  protected override Money CalculateExtendedPrice(ILineItem lineItem, Currency currency) {
    return new Money(0, currency);
  }

  protected override Money CalculateSalesTax(ILineItem lineItem, IMarket market, Currency currency, IOrderAddress shippingAddress) {
    return new Money(0, currency);
  }
}

Change the default validation

The default implementation validates that the extended price and sales tax are non-negative after calculation. To change the behavior, override the ValidateExtendedPrice and ValidateSalesTax methods.

public class LineItemCalculatorSample: DefaultLineItemCalculator {
  protected override void ValidateExtendedPrice(Money money) {
    if (money.Amount < 0) {
      throw new ValidationException("Extended price must not be negative.");
    }
  }

  protected override void ValidateSalesTax(Money money) {
    if (money.Amount < 0) {
      throw new ValidationException("Sales tax must not be negative.");
    }
  }
}