Example of Domain Events using MediatR

Directory.Packages.props

@@ -48,7 +48,8 @@
     </PackageVersion>
     <PackageVersion Include="Microsoft.VisualStudio.Azure.Containers.Tools.Targets" Version="1.21.0" />
     <PackageVersion Include="Microsoft.Win32.Primitives" Version="4.3.0" />
-    <PackageVersion Include="MinimalApi.Endpoint" Version="1.3.0" />
+    <PackageVersion Include="Minimalpi.Endpoint" Version="1.3.0" />
+    <PackageVersion Include="NimblePros.SharedKernel" Version="2.1.1" />
     <PackageVersion Include="NimblePros.Metronome" Version="0.4.1" />
     <PackageVersion Include="NSubstitute" Version="5.3.0" />
     <PackageVersion Include="NSubstitute.Analyzers.CSharp" Version="1.0.17" />

src/ApplicationCore/ApplicationCore.csproj

@@ -8,8 +8,9 @@
 	<ItemGroup>
 		<PackageReference Include="Ardalis.GuardClauses" />
 		<PackageReference Include="Ardalis.Result" />
-		<PackageReference Include="Ardalis.Specification" />		
-		<PackageReference Include="System.Security.Claims" />
+		<PackageReference Include="Ardalis.Specification" />
+    <PackageReference Include="NimblePros.SharedKernel" />
+    <PackageReference Include="System.Security.Claims" />
 		<PackageReference Include="System.Text.Json" />
 	</ItemGroup>
 

src/ApplicationCore/Entities/OrderAggregate/Events/OrderCreatedEvent.cs

@@ -0,0 +1,7 @@
+using Ardalis.SharedKernel;
+
+namespace Microsoft.eShopWeb.ApplicationCore.Entities.OrderAggregate.Events;
+public class OrderCreatedEvent(Order order) : DomainEventBase
+{
+    public Order Order { get; init; } = order;
+}

src/ApplicationCore/Entities/OrderAggregate/Handlers/OrderCreatedHandler.cs

@@ -0,0 +1,20 @@
+using System.Threading;
+using System.Threading.Tasks;
+using MediatR;
+using Microsoft.eShopWeb.ApplicationCore.Entities.OrderAggregate.Events;
+using Microsoft.eShopWeb.ApplicationCore.Interfaces;
+using Microsoft.Extensions.Logging;
+
+namespace Microsoft.eShopWeb.ApplicationCore.Entities.OrderAggregate.Handlers;
+
+public class OrderCreatedHandler(ILogger<OrderCreatedHandler> logger, IEmailSender emailSender) : INotificationHandler<OrderCreatedEvent>
+{
+    public async Task Handle(OrderCreatedEvent domainEvent, CancellationToken cancellationToken)
+    {
+        logger.LogInformation("Order #{orderId} placed: ", domainEvent.Order.Id);
+
+        await emailSender.SendEmailAsync("[email protected]",
+                                         "Order Created",
+                                         $"Order with id {domainEvent.Order.Id} was created.");
+    }
+}

src/ApplicationCore/Services/OrderService.cs

@@ -1,9 +1,11 @@
 using System.Linq;
 using System.Threading.Tasks;
 using Ardalis.GuardClauses;
+using MediatR;
 using Microsoft.eShopWeb.ApplicationCore.Entities;
 using Microsoft.eShopWeb.ApplicationCore.Entities.BasketAggregate;
 using Microsoft.eShopWeb.ApplicationCore.Entities.OrderAggregate;
+using Microsoft.eShopWeb.ApplicationCore.Entities.OrderAggregate.Events;
 using Microsoft.eShopWeb.ApplicationCore.Interfaces;
 using Microsoft.eShopWeb.ApplicationCore.Specifications;
 
@@ -15,16 +17,18 @@ public class OrderService : IOrderService
     private readonly IUriComposer _uriComposer;
     private readonly IRepository<Basket> _basketRepository;
     private readonly IRepository<CatalogItem> _itemRepository;
+    private readonly IMediator _mediator;
 
     public OrderService(IRepository<Basket> basketRepository,
         IRepository<CatalogItem> itemRepository,
         IRepository<Order> orderRepository,
-        IUriComposer uriComposer)
+        IUriComposer uriComposer, IMediator mediator)
     {
         _orderRepository = orderRepository;
         _uriComposer = uriComposer;
         _basketRepository = basketRepository;
         _itemRepository = itemRepository;
+        _mediator = mediator;
     }
 
     public async Task CreateOrderAsync(int basketId, Address shippingAddress)
@@ -49,5 +53,7 @@ public async Task CreateOrderAsync(int basketId, Address shippingAddress)
         var order = new Order(basket.BuyerId, shippingAddress, items);
 
         await _orderRepository.AddAsync(order);
+        OrderCreatedEvent orderCreatedEvent = new OrderCreatedEvent(order);
+        await _mediator.Publish(orderCreatedEvent);
     }
 }

src/Infrastructure/Services/LoggerEmailSender.cs

@@ -0,0 +1,13 @@
+using System.Threading.Tasks;
+using Microsoft.eShopWeb.ApplicationCore.Interfaces;
+
+namespace Microsoft.eShopWeb.Infrastructure.Services;
+
+public class LoggerEmailSender(IAppLogger<LoggerEmailSender> logger): IEmailSender
+{
+    public Task SendEmailAsync(string email, string subject, string message)
+    {
+        logger.LogInformation("to: {email}, subject: {emailSubject}, message: {emailMessage}", email, subject, message);
+        return Task.CompletedTask;
+    }
+}

src/Web/Configuration/ConfigureCoreServices.cs

@@ -23,7 +23,7 @@ public static IServiceCollection AddCoreServices(this IServiceCollection service
         services.AddSingleton<IUriComposer>(new UriComposer(catalogSettings));
 
         services.AddScoped(typeof(IAppLogger<>), typeof(LoggerAdapter<>));
-        services.AddTransient<IEmailSender, EmailSender>();
+        services.AddTransient<IEmailSender, LoggerEmailSender>();
 
         return services;
     }

src/Web/Configuration/ConfigureWebServices.cs

@@ -1,4 +1,5 @@
-using Microsoft.eShopWeb.Web.Interfaces;
+using Microsoft.eShopWeb.ApplicationCore.Services;
+using Microsoft.eShopWeb.Web.Interfaces;
 using Microsoft.eShopWeb.Web.Services;
 
 namespace Microsoft.eShopWeb.Web.Configuration;
@@ -7,8 +8,13 @@ public static class ConfigureWebServices
 {
     public static IServiceCollection AddWebServices(this IServiceCollection services, IConfiguration configuration)
     {
-        services.AddMediatR(cfg => 
-            cfg.RegisterServicesFromAssembly(typeof(BasketViewModelService).Assembly));
+        // Add MediatR support for the services
+        services.AddMediatR(cfg =>
+        {
+            cfg.RegisterServicesFromAssembly(typeof(BasketViewModelService).Assembly);
+            cfg.RegisterServicesFromAssembly(typeof(OrderService).Assembly);
+        }
+        );
         services.AddScoped<IBasketViewModelService, BasketViewModelService>();
         services.AddScoped<CatalogViewModelService>();
         services.AddScoped<ICatalogItemViewModelService, CatalogItemViewModelService>();