Minimal APIs in ASP.NET Core .NET 8

Introduction

Minimal APIs map routes to lambdas or methods in Program.cs — ideal for ShopNest microservices (inventory snapshot, health probes) without full controller ceremony.

After this article you will

• Map GET/POST/PUT/DELETE with MapGroup
• Bind route, query, and body parameters
• Inject services into route handlers
• Add filters and OpenAPI to minimal endpoints
• Compare minimal vs controller-based APIs

Prerequisites

• Article 41 — HTTP Client and External APIs
• ShopNest with EF Core and auth from Modules 2–4

Concept deep-dive

var inventory = app.MapGroup("/api/inventory").WithTags("Inventory");

inventory.MapGet("/", async (IInventoryService svc) =>
    Results.Ok(await svc.GetAllAsync()));

inventory.MapGet("/{sku}", async (string sku, IInventoryService svc) =>
{
    var item = await svc.GetBySkuAsync(sku);
    return item is null ? Results.NotFound() : Results.Ok(item);
});

inventory.MapPost("/", async (CreateInventoryDto dto, IInventoryService svc) =>
{
    var created = await svc.CreateAsync(dto);
    return Results.Created($"/api/inventory/{created.Sku}", created);
}).RequireAuthorization();

Hands-on — ShopNest Lightweight Microservice

1. ShopNest.InventoryService — minimal API only project.
2. MapGroup with route prefix and OpenAPI tag.
3. Validation filter or Validate on POST.
4. Dockerfile for lightweight container deploy.

Common errors & best practices

• Giant Program.cs — use extension methods MapInventoryEndpoints().
• Skipping authorization on write endpoints.

Interview questions

Q: When Minimal APIs?
A: Small services, BFFs, internal tools — not mandatory for all ShopNest APIs.

Q: DI in minimal handlers?
A: Parameters resolved from DI like controller constructors.

Summary

• Minimal APIs reduce ceremony for small services
• MapGroup organizes related endpoints
• Same auth, validation, OpenAPI as controllers
• ShopNest inventory microservice is ideal use case

Previous: HTTP Client and External APIs
Next: SignalR — Real-Time Web Applications

FAQ