C# Academy · Lesson

Creating Your First Minimal API

Bootstrap a Minimal API project, define route handlers, and return typed results with minimal boilerplate.

Creating Your First Minimal API is a free C# Academy lesson on CoddyKit — lesson 1 of 4. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the C# Academy learning path, one of 4 lessons in the course, and your progress syncs across the web and the CoddyKit app.

What Are Minimal APIs?

Minimal APIs, introduced in .NET 6, let you build HTTP endpoints with minimal ceremony — no controllers, no action attributes, just route handlers defined directly in Program.cs. They're ideal for microservices and lightweight APIs.

The Simplest Minimal API

A complete HTTP API in just a few lines. The MapGet, MapPost, MapPut, and MapDelete methods define route handlers for each HTTP verb.

var builder = WebApplication.CreateBuilder(args);
var app = builder.Build();

app.MapGet("/", () => "Hello, Minimal API!");
app.MapGet("/ping", () => Results.Ok(new { status = "pong" }));

app.Run();
// That's it — no Startup.cs, no controllers

Typed Results for Proper HTTP Responses

Use Results or TypedResults for correct HTTP status codes and content types. TypedResults is preferred for OpenAPI schema inference.

app.MapGet("/products/{id}", async (int id, AppDbContext db) =>
{
    var product = await db.Products.FindAsync(id);
    return product is null
        ? Results.NotFound()
        : Results.Ok(product);
});

app.MapPost("/products", async (Product product, AppDbContext db) =>
{
    db.Products.Add(product);
    await db.SaveChangesAsync();
    return Results.Created($"/products/{product.Id}", product);
});

Route Parameters & Query Strings

Route parameters are captured from the URL path, query string parameters are automatically bound from the query, and the request body is deserialized from JSON.

// Route param {id} + query param ?includeDeleted
app.MapGet("/orders/{id}", async (
    int id,
    bool includeDeleted = false,
    AppDbContext db) =>
{
    var query = db.Orders.AsQueryable();
    if (!includeDeleted) query = query.Where(o => !o.IsDeleted);
    var order = await query.FirstOrDefaultAsync(o => o.Id == id);
    return order is null ? Results.NotFound() : Results.Ok(order);
});

Dependency Injection in Route Handlers

Services registered in the DI container can be injected directly as route handler parameters. The framework resolves them automatically.

builder.Services.AddScoped<ProductService>();

app.MapGet("/products", async (ProductService svc) =>
{
    var products = await svc.GetAllAsync();
    return Results.Ok(products);
});

app.MapDelete("/products/{id}", async (int id, ProductService svc) =>
{
    var deleted = await svc.DeleteAsync(id);
    return deleted ? Results.NoContent() : Results.NotFound();
});

Request Body Binding

Parameters that match registered services are injected; everything else is bound from the request body (JSON by default). Use [FromBody] explicitly if needed.

record CreateProductRequest(string Name, decimal Price, int Stock);

app.MapPost("/products", async (
    CreateProductRequest req,
    ProductService svc) =>
{
    var product = await svc.CreateAsync(req.Name, req.Price, req.Stock);
    return TypedResults.Created($"/products/{product.Id}", product);
});

Returning Different Status Codes

Results provides factory methods for all common HTTP responses. Use them for semantically correct REST APIs.

app.MapPut("/products/{id}", async (int id, Product update, AppDbContext db) =>
{
    var existing = await db.Products.FindAsync(id);
    if (existing is null) return Results.NotFound();

    existing.Name  = update.Name;
    existing.Price = update.Price;
    await db.SaveChangesAsync();
    return Results.Ok(existing);
});

// Other useful Results:
// Results.BadRequest("message")
// Results.Conflict()
// Results.UnprocessableEntity(errors)
// Results.Accepted()

Adding Metadata with WithName & WithTags

Attach metadata to endpoints to improve documentation and routing. Use WithName, WithTags, and WithSummary for organized OpenAPI output.

app.MapGet("/products/{id}", GetProduct)
   .WithName("GetProductById")
   .WithTags("Products")
   .WithSummary("Retrieves a product by its ID")
   .Produces<Product>()
   .Produces(404);

static async Task<IResult> GetProduct(int id, AppDbContext db)
{
    var p = await db.Products.FindAsync(id);
    return p is null ? Results.NotFound() : Results.Ok(p);
}

Authorization in Minimal APIs

Apply RequireAuthorization() to protect endpoints, or use AllowAnonymous() to opt out. Policies work the same as in controllers.

builder.Services.AddAuthentication().AddJwtBearer();
builder.Services.AddAuthorization();

app.UseAuthentication();
app.UseAuthorization();

app.MapGet("/profile", (ClaimsPrincipal user) =>
    Results.Ok(user.Identity!.Name))
   .RequireAuthorization();

app.MapGet("/public", () => "No auth needed")
   .AllowAnonymous();

Organizing with Static Methods

For larger APIs, move route handlers to static methods or extension methods to keep Program.cs clean and navigable.

// Extension method groups endpoints by feature
public static class ProductEndpoints
{
    public static void MapProductEndpoints(this WebApplication app)
    {
        app.MapGet("/products",    GetAll);
        app.MapGet("/products/{id}", GetById);
        app.MapPost("/products",   Create);
    }

    private static async Task<IResult> GetAll(AppDbContext db)
        => Results.Ok(await db.Products.AsNoTracking().ToListAsync());

    // ... other handlers
}

// In Program.cs:
app.MapProductEndpoints();

Real-World: Full CRUD Minimal API

A complete minimal CRUD API for a Todo resource — concise, testable, and production-ready.

app.MapGet("/todos", async (AppDbContext db) =>
    Results.Ok(await db.Todos.AsNoTracking().ToListAsync()));

app.MapGet("/todos/{id}", async (int id, AppDbContext db) =>
{
    var todo = await db.Todos.FindAsync(id);
    return todo is null ? Results.NotFound() : Results.Ok(todo);
});

app.MapPost("/todos", async (Todo todo, AppDbContext db) =>
{
    db.Todos.Add(todo);
    await db.SaveChangesAsync();
    return Results.Created($"/todos/{todo.Id}", todo);
});

app.MapDelete("/todos/{id}", async (int id, AppDbContext db) =>
{
    int n = await db.Todos.Where(t => t.Id == id).ExecuteDeleteAsync();
    return n > 0 ? Results.NoContent() : Results.NotFound();
});

Quick Check

How does a Minimal API route handler receive a registered DI service?

Recap: Creating Your First Minimal API

Key takeaways:

MapGet/Post/Put/Delete define route handlers directly in Program.cs
Use Results / TypedResults for correct HTTP status codes
Route, query, body, and DI parameters are all bound automatically
Use RequireAuthorization() and AllowAnonymous() for auth
Organize large APIs with extension methods or route groups

Frequently asked questions

Is the “Creating Your First Minimal API” lesson free?

Yes — the full text of “Creating Your First Minimal API” is free to read here on the web, and the C# Academy course includes 4 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the C# Academy course, upgrade to CoddyKit PRO.

What will I learn in “Creating Your First Minimal API”?

Bootstrap a Minimal API project, define route handlers, and return typed results with minimal boilerplate. You practise C# Academy with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.

Do I need any experience to start C# Academy?

No prior experience is required. C# Academy on CoddyKit is structured for beginners through advanced learners; this is — lesson 1 of 4, so you can start here or from the beginning and move at your own pace.

How long does the “Creating Your First Minimal API” lesson take?

Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.

Can I write and run code in this C# Academy lesson?

Yes. Every C# Academy lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.

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