Why should you care?

Order.Api must notify Payment without waiting. RabbitMQ decouples services in time and failure domains.

See it live — copy this example

Create a Web API project (dotnet new webapi), paste the code, then run dotnet run.

builder.Services.AddMassTransit(x =>
{
    x.UsingRabbitMq((ctx, cfg) =>
    {
        cfg.Host("localhost", "/", h => { h.Username("guest"); h.Password("guest"); });
        cfg.ConfigureEndpoints(ctx);
    });
    x.AddConsumer<OrderPlacedConsumer>();
});

// Publish from Order.Api
await _publishEndpoint.Publish(new OrderPlacedEvent(order.Id, order.CustomerId, order.Total));

Run Example »

Edit the code and click Run — like W3Schools Try it Yourself.

What happened?

• MassTransit configures RabbitMQ host, serializers, and consumer endpoints.
• Publish is fire-and-forget from HTTP handler after DB commit.

Try it yourself

1. Install MassTransit.RabbitMQ NuGet.
2. Add OrderPlacedEvent record in Contracts project.
3. Publish after SaveChanges in POST /orders.
4. Change a string or route in the example and save — watch Swagger or the RabbitMQ Management UI update.
5. Break the code on purpose (remove a semicolon), read the error message, then fix it.

Remember

MassTransit simplifies RabbitMQ in .NET. Publish after successful save. Consumers live in same or separate host.