This sample demonstrates:
- a simple application running on .NET Core 3.1
- how to integrate NServiceBus with an ASP.NET Core Web API project
- a simple back-end process running in the .NET Core generic host
- the built-in tools used to inject dependencies into message handler classes
NServiceBus.MicrosoftLogging community NuGet package should be installed to use the Microsoft.Extensions.Logging library.Front-end
The front-end project hosts a simple web page that contains a form. When the form is submitted, a message is sent to the back-end application via NServiceBus for processing.
The front-end uses the .NET Core generic host to host an NServiceBus endpoint and ASP.NET Core WebAPI controllers. The endpoint is configured as a send only endpoint as it does not need to process any messages. There is routing configured for a single message type; SomeMessage messages get routed to Sample..
public static void Main(string[] args)
{
CreateHostBuilder(args).Build().Run();
}
public static IHostBuilder CreateHostBuilder(string[] args) =>
Host.CreateDefaultBuilder(args)
.UseNServiceBus(context =>
{
var endpointConfiguration = new EndpointConfiguration("Sample.FrontEnd");
endpointConfiguration.SendOnly();
var routing = endpointConfiguration.UseTransport(new LearningTransport());
routing.RouteToEndpoint(typeof(SomeMessage), "Sample.BackEnd");
return endpointConfiguration;
})
.ConfigureWebHostDefaults(webBuilder =>
{
webBuilder.UseStartup<Startup>();
})
;
The WebAPI controller is able to take a dependency on IMessageSession and use it to send messages to the backend.
public class HomeController : Controller
{
IMessageSession messageSession;
public HomeController(IMessageSession messageSession)
{
this.messageSession = messageSession;
}
public ActionResult Index()
{
return View();
}
[HttpPost]
public async Task<ActionResult> Index(ViewModel model)
{
if (!ModelState.IsValid)
{
return View(model);
}
await messageSession.Send(new SomeMessage { Number = model.Number })
.ConfigureAwait(false);
ViewBag.Message = "Request was queued successfully.";
return View(model);
}
}
Back-end
The back-end project hosts an NServiceBus endpoint which processes messages sent from the front-end. When handling each message it relies on a service that is registered with the host's service collection.
The back-end uses the same API as the front-end to register an NServiceBus endpoint with the generic host.
builder.UseNServiceBus(ctx =>
{
var endpointConfiguration = new EndpointConfiguration("Sample.BackEnd");
endpointConfiguration.UseTransport(new LearningTransport());
endpointConfiguration.DefineCriticalErrorAction(OnCriticalError);
return endpointConfiguration;
});
Additionally, it registers an important calculation service with the host's service collection.
builder.ConfigureServices(services =>
{
services.AddSingleton<ICalculateStuff, CalculateStuff>();
});
The NServiceBus message handler is able to take a dependency on the registered service and use it when handling the message.
public class SomeHandler : IHandleMessages<SomeMessage>
{
private readonly ICalculateStuff stuffCalculator;
public SomeHandler(ICalculateStuff stuffCalculator)
{
this.stuffCalculator = stuffCalculator;
}
public async Task Handle(SomeMessage message, IMessageHandlerContext context)
{
await stuffCalculator.Calculate(message.Number);
// Do some more stuff if needed
}
}