Most enterprise applications have a need for a simple in-memory event bus which implements the observer pattern through the pub/sub pattern. RCommon implements a simple dependency-free event bus for this utility but there are some advantages to using MediatR. MediatR is a mediator pattern implementation which can be used as an event bus. MediatR is a mature library and allows developers to use aspect oriented concepts to manipulate the request pipeline.
Configuration
using Examples.EventHandling.MediatR;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using RCommon;
using RCommon.EventHandling.Producers;
using RCommon.MediatR;
using RCommon.MediatR.Producers;
using System.Diagnostics;
using System.Reflection;
using static System.Net.Mime.MediaTypeNames;
try
{
var host = Host.CreateDefaultBuilder(args)
.ConfigureAppConfiguration((context, builder) =>
{
ConfigurationContainer.Configuration = builder
.Build();
})
.ConfigureServices(services =>
{
// Configure RCommon
services.AddRCommon()
.WithEventHandling<MediatREventHandlingBuilder>(eventHandling =>
{
eventHandling.AddProducer<PublishWithMediatREventProducer>();
eventHandling.AddSubscriber<TestEvent, TestEventHandler>();
});
}).Build();
}
catch (Exception ex)
{
Console.WriteLine(ex.ToString());
}
Implementation
The implementation details for how you produce and subscribe to events will not change due to a consistent producer/subscriber API in RCommon.
Producing the Event
Console.WriteLine("Example Starting");
var eventProducers = host.Services.GetServices<IEventProducer>();
var testEvent = new TestEvent(DateTime.Now, Guid.NewGuid());
foreach (var producer in eventProducers)
{
Console.WriteLine($"Producer: {producer}");
await producer.ProduceEventAsync(testEvent);
}
Console.WriteLine("Example Complete");
Console.ReadLine();
Subscribing to the Event
using RCommon.EventHandling.Subscribers;
using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace Examples.EventHandling.MediatR
{
public class TestEventHandler : ISubscriber<TestEvent>
{
public TestEventHandler()
{
}
public async Task HandleAsync(TestEvent notification, CancellationToken cancellationToken = default)
{
Console.WriteLine("I just handled this event {0}", new object[] { notification.ToString() });
await Task.CompletedTask;
}
}
}