How to Merge Anonymous Carts When a Customer Logs In with Optimizely Commerce 14

In e-commerce, it is common for users to browse a site anonymously, adding items to their cart without creating an account. Later, when the user decides to create an account or log in, they may have items already in their anonymous cart that they would like to keep. In this scenario, it is important to merge the anonymous cart with the authenticated cart to ensure a seamless shopping experience.

In this blog post, I will show you how to merge anonymous carts with authenticated carts in Optimizely Commerce 14.

Overview

The code I will be using is a middleware component that runs on every incoming HTTP request. If the user is authenticated, the middleware retrieves the user's anonymous cart using the IAnonymousIdFeature and merges it with their authenticated cart.

using EPiServer.Commerce.Order;
using EPiServer.ServiceLocation;
using Mediachase.Commerce;
using Mediachase.Commerce.Anonymous;
using Mediachase.Commerce.Customers;
using Mediachase.Commerce.Markets;

namespace Infrastructure.Commerce.Extensions
{
    public class AnonymousCartMergingMiddleware
    {
        private readonly RequestDelegate _next;

        public AnonymousCartMergingMiddleware(RequestDelegate next)
        {
            _next = next;
        }

        public async Task InvokeAsync(HttpContext context)
        {
            if (context.User.Identity != null && context.User.Identity.IsAuthenticated)
            {
                var anonymousId = context.Features.Get<IAnonymousIdFeature>().AnonymousId;
                
                if (!string.IsNullOrWhiteSpace(anonymousId))
                {
                    var orderRepository = ServiceLocator.Current.GetInstance<IOrderRepository>();
                    var marketService = ServiceLocator.Current.GetInstance<IMarketService>();
                    
                    var market = marketService.GetMarket(MarketId.Default);
                    var cart = orderRepository.LoadCart<ICart>(new Guid(anonymousId), Constants.CartName.ShoppingCart, market.MarketId);

                    if (cart != null && cart.GetAllLineItems().ToList().Count > 0)
                    {
                        var currentMarket = ServiceLocator.Current.GetInstance<ICurrentMarket>();
                        cart.MarketId = currentMarket.GetCurrentMarket().MarketId;
                        orderRepository.Save(cart);
                        
                        var profileMigrator = ServiceLocator.Current.GetInstance<IProfileMigrator>();
                        profileMigrator.MigrateCarts(new Guid(anonymousId));
                    }
                }
            }

            await _next(context);
        }
    }
}

You can use an extension method to expose the middleware through `IApplicationBuilder`.

namespace Infrastructure.Commerce.Extensions
{
    public static class AnonymousCartMergingMiddlewareExtensions
    {
        public static IApplicationBuilder UseAnonymousCartMerging(this IApplicationBuilder builder)
        {
            return builder.UseMiddleware<AnonymousCartMergingMiddleware>();
        }
    }
}

The following code calls the middleware from `Startup.cs`

    public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
    {
        app.UseAnonymousCartMerging();        
    }