Dotnet | Minimal API

A Minimal API lets you define endpoints directly in Program.cs using simple methods.

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Example

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

app.MapGet("/", () => "Hello World");

app.MapGet("/products/{id}", (int id) =>
{
    return $"Product Id: {id}";
});

app.Run();

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What’s happening?

• MapGet → defines an HTTP GET endpoint
• No controller, no action methods
• Everything is defined inline

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Key Features

1. Less boilerplate

No need for:

• Controllers
• Attributes like [HttpGet]

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2. Fast to build

• Great for small APIs
• Quick prototypes

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3. Built-in dependency injection

app.MapGet("/data", (IMyService service) =>
{
    return service.GetData();
});

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4. Supports all HTTP methods

app.MapPost("/products", (Product p) => { });
app.MapPut("/products/{id}", (int id) => { });
app.MapDelete("/products/{id}", (int id) => { });

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Minimal API vs Controller API

Feature	Minimal API	Controller API
Code size	Very small	More boilerplate
Structure	Flat	Layered (Controllers)
Best for	Small / simple APIs	Large / enterprise apps
Flexibility	Moderate	High

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When to Use Minimal API?

Good for:

• Microservices
• Simple CRUD APIs
• Prototypes
• Serverless functions

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Not ideal for:

• Large complex applications
• Apps needing strict architecture (Controllers, Filters, etc.)

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Real-World Example

app.MapGet("/users/{id}", async (int id, AppDbContext db) =>
{
    var user = await db.Users.FindAsync(id);
    return user is not null ? Results.Ok(user) : Results.NotFound();
});

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Analogy

• Minimal API = writing a quick note 
• Controller API = writing a structured document 

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Key Takeaway

Minimal API:

• Removes ceremony
• Focuses on simplicity and speed
• Still uses full power of ASP.NET Core under the hood