Implement Custom Pricing Rules

Why custom pricing rules matter

Standard price lists cover most scenarios, but real-world pricing often requires logic that goes beyond static price entries. You may need to calculate prices based on external feeds, apply contract-specific rates, adjust prices by time of day, or combine multiple data sources into a final price. Commerce exposes its pricing through an extensible pipeline that you can customize without replacing the entire pricing system.

This guide covers implementing a custom price service, building dynamic pricing logic, and plugging into the price resolver pipeline.

What you will do

1. Understand the price resolution pipeline
2. Implement a custom IPriceService for dynamic pricing
3. Build a price resolver filter for conditional adjustments
4. Register and test custom pricing components

Understand the price resolution pipeline

When Commerce resolves a price, it follows a pipeline:

1. IPriceService returns candidate prices from price lists
2. IPriceOptimizer selects the best price based on customer context
3. Promotion engine applies any applicable discounts

You can extend any step. The most common extension points are implementing a custom IPriceService for external price sources and adding filters to modify resolved prices.

Implement a custom IPriceService

Replace or decorate the default price service to pull prices from an external system (ERP, PIM, or pricing engine).

Custom price service with external data

C# (.NET)

csharp Copy

using Mediachase.Commerce;
using Mediachase.Commerce.Pricing;

public class ExternalPriceService : IPriceService
{
    private readonly IPriceService _defaultService;
    private readonly IExternalPriceApi _externalApi;

    public ExternalPriceService(
        IPriceService defaultService,
        IExternalPriceApi externalApi)
    {
        _defaultService = defaultService;
        _externalApi = externalApi;
    }

    public IPriceValue GetDefaultPrice(
        MarketId marketId, DateTime validOn,
        CatalogKey catalogKey, Currency currency)
    {
        // Try external source first
        var externalPrice = _externalApi
            .GetPrice(catalogKey.CatalogEntryCode,
                marketId.Value, currency.CurrencyCode);

        if (externalPrice.HasValue)
        {
            return new PriceValue
            {
                CatalogKey = catalogKey,
                MarketId = marketId,
                UnitPrice = new Money(
                    externalPrice.Value, currency),
                CustomerPricing =
                    CustomerPricing.AllCustomers,
                ValidFrom = DateTime.UtcNow,
                ValidUntil = null,
                MinQuantity = 0
            };
        }

        // Fall back to built-in prices
        return _defaultService.GetDefaultPrice(
            marketId, validOn, catalogKey, currency);
    }

    public IEnumerable<IPriceValue> GetPrices(
        MarketId marketId, DateTime validOn,
        CatalogKey catalogKey,
        PriceFilter filter)
    {
        return _defaultService.GetPrices(
            marketId, validOn, catalogKey, filter);
    }

    public IEnumerable<IPriceValue> GetCatalogEntryPrices(
        IEnumerable<CatalogKey> catalogKeys)
    {
        return _defaultService
            .GetCatalogEntryPrices(catalogKeys);
    }
}

Build a price resolver filter

For conditional adjustments (loyalty discounts, time-based pricing, contract rates), implement a filter that modifies the resolved price.

Dynamic pricing filter

C# (.NET)

csharp Copy

using Mediachase.Commerce;
using Mediachase.Commerce.Pricing;

public class LoyaltyPriceFilter
{
    private readonly ICustomerGroupService
        _groupService;

    public LoyaltyPriceFilter(
        ICustomerGroupService groupService)
    {
        _groupService = groupService;
    }

    public IPriceValue AdjustPrice(
        IPriceValue originalPrice,
        Guid customerId)
    {
        var loyaltyTier = _groupService
            .GetLoyaltyTier(customerId);

        decimal discount = loyaltyTier switch
        {
            "Gold" => 0.10m,
            "Platinum" => 0.15m,
            "Diamond" => 0.20m,
            _ => 0m
        };

        if (discount == 0m)
            return originalPrice;

        var adjustedAmount = originalPrice
            .UnitPrice.Amount * (1 - discount);

        return new PriceValue
        {
            CatalogKey = originalPrice.CatalogKey,
            MarketId = originalPrice.MarketId,
            UnitPrice = new Money(adjustedAmount,
                originalPrice.UnitPrice.Currency),
            CustomerPricing =
                originalPrice.CustomerPricing,
            ValidFrom = originalPrice.ValidFrom,
            ValidUntil = originalPrice.ValidUntil,
            MinQuantity = originalPrice.MinQuantity
        };
    }
}

Register custom pricing components

Register your custom services using dependency injection so Commerce uses them instead of (or alongside) the defaults.

Service registration

C# (.NET)

csharp Copy

using Microsoft.Extensions.DependencyInjection;

public static class PricingServiceRegistration
{
    public static IServiceCollection
        AddCustomPricing(
            this IServiceCollection services)
    {
        // Decorate the default IPriceService
        services.Decorate<IPriceService,
            ExternalPriceService>();

        // Register the loyalty filter
        services.AddSingleton<LoyaltyPriceFilter>();

        // Register the external API client
        services.AddHttpClient<IExternalPriceApi,
            ExternalPriceApi>(client =>
        {
            client.BaseAddress = new Uri(
                "https://pricing.example.com/api/");
            client.Timeout = TimeSpan.FromSeconds(5);
        });

        return services;
    }
}

Key design decisions:

Approach	When to use
Decorate IPriceService	External price source that replaces or augments stored prices
Price filter	Conditional adjustments based on customer context
Custom IPriceOptimizer	Change how Commerce selects among multiple candidate prices
Promotion engine extension	Discounts that should appear as promotions in the cart

Common issues

Issue	Cause	Fix
Custom prices not appearing	Service not registered or decorator order incorrect	Verify DI registration and ensure your decorator wraps the default service
External API timeout slowing page loads	No caching on external price calls	Add a short-lived cache (30-60 seconds) around external price lookups
Price shows original amount, not adjusted	Filter not called in the resolution pipeline	Ensure your filter is invoked after the default price resolution
Negative prices after discount	Discount percentage exceeds 100%	Add a floor check (Math.Max(0, adjustedAmount)) in your filter

Related content

Continue your journey with these related pages.

📖Understand the concepts

• Optimizely Commerce

🔧Follow a guide

• Configure Customer Group Pricing
• Set Up Promotions