Why should you care?

Orders tie together user, products, payment, and inventory. Owning order state in one service gives one place to answer "where is my order?"

See it live — copy this example

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

app.MapPost("/orders", async (CreateOrderDto dto, OrderDbContext db) =>
{
    var order = new Order
    {
        Id = Guid.NewGuid(),
        CustomerId = dto.CustomerId,
        Status = "Created",
        Lines = dto.Lines.Select(l => new OrderLine
        {
            ProductId = l.ProductId,
            Qty = l.Qty,
            UnitPrice = l.UnitPrice
        }).ToList()
    };
    order.Total = order.Lines.Sum(l => l.Qty * l.UnitPrice);
    db.Orders.Add(order);
    await db.SaveChangesAsync();
    return Results.Created($"/orders/{order.Id}", order);
});

Run Example »

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

What happened?

• Order stores line prices at order time — catalog price may change tomorrow.
• Status starts Created; Payment service will move it to Paid later.

Try it yourself

1. Create Order entity with OrderLines collection.
2. POST /orders with customerId and lines array.
3. GET /orders/{id} to fetch status.
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

Order service owns order aggregate and status. Snapshot prices on lines. Payment and inventory react in later lessons via HTTP or events.

Real-world: Flipkart order tracking

Customer sees Created → Paid → Packed → Shipped. Each status change may come from different services but Order owns the timeline.

Outcome: Support team queries Order.Api — not Payment or Warehouse directly.