.NET Minimal APIs – The Simplified Path to Web Development

Less Boilerplate, Cleaner Code, Faster Maintenance

What Are Minimal APIs?

Minimal APIs streamline the development of .NET applications by eliminating the need for extensive boilerplate code. Unlike the traditional ASP.NET MVC model, which separates controllers, models, and views into distinct folders, Minimal APIs allow developers to define endpoints directly in the Program.cs file.

Key Characteristics of Minimal APIs:

• Endpoint-Focused: Define routes and logic directly without the need for controllers.
• Less Boilerplate: No need for additional classes, attributes, or configurations.
• Integrated with Middleware: Combine routing, middleware, and logic seamlessly.
• Optimized for Microservices Architecture: A perfect fit for lightweight and modular services.
• Built for Simplicity: Ideal for small RESTful APIs or rapid .NET application development.

How Minimal APIs Simplify Code and Maintenance

1. Compact and Readable Codebase

• All critical logic for a small API can reside in a single file (Program.cs), making it easy to locate and modify.
• By reducing the number of classes, files, and dependencies, developers can focus on the business logic without unnecessary overhead.

2. Faster Prototyping

• Start with just a few lines of code to get a working API.
• Great for proof-of-concept projects, where a fast time-to-market is critical.

3. Reduced Overhead for Small Apps

• Traditional ASP.NET MVC projects might be overkill for small APIs or microservices. Minimal APIs provide a leaner alternative while maintaining robustness.

4. Easier Onboarding

• New team members or junior developers can quickly grasp the structure since no complex folder or class hierarchy exists.

5. Clean Dependency Injection

• Services are configured in one place and passed directly into endpoints as needed, simplifying .NET software development.

Minimal APIs in Action – A Simple Example

Here’s how to create a Minimal API in .NET to manage a list of books:

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;

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

// In-memory data store
var books = new List<Book>
{
    new Book(1, "C# in Depth", "Jon Skeet"),
    new Book(2, "Pro ASP.NET Core", "Adam Freeman")
};

// GET all books
app.MapGet("/books", () => Results.Ok(books));

// GET a book by ID
app.MapGet("/books/{id:int}", (int id) =>
{
    var book = books.FirstOrDefault(b => b.Id == id);
    return book is not null ? Results.Ok(book) : Results.NotFound();
});

// POST to add a new book
app.MapPost("/books", (Book newBook) =>
{
    books.Add(newBook);
    return Results.Created($"/books/{newBook.Id}", newBook);
});

// DELETE a book by ID
app.MapDelete("/books/{id:int}", (int id) =>
{
    var book = books.FirstOrDefault(b => b.Id == id);
    if (book is null) return Results.NotFound();
    
    books.Remove(book);
    return Results.NoContent();
});

app.Run();

record Book(int Id, string Title, string Author);

How This Simplifies Code and Maintenance

• Single-File Simplicity: The entire API logic is defined in one place, making it easier to read, debug, and extend.
• Clear Endpoint Definitions: Routes (GET /books, POST /books) are explicitly defined, making the API behavior straightforward.
• Built-In HTTP Results: Results.Ok(), Results.NotFound(), and other result types streamline responses, keeping code concise.
• No Scaffolding or Attributes: No need for controller classes or [HttpGet]/[HttpPost] attributes.
• Seamless Dependency Injection: Services can be injected directly into handlers without requiring constructor injection.

When to Use Minimal APIs

• Perfect for microservices, serverless functions, or simple RESTful APIs.
• It is ideal for prototyping or applications with a small number of endpoints.
• Works great for IoT backends or APIs consumed by single-page applications (SPAs).

Real-World Example: Microservices with Minimal APIs

If you are developing a microservice that processes order data for an e-commerce platform, Minimal APIs allow you to quickly define routes like /orders, /orders/{id}, and /orders/status without unnecessary complexity. This approach enables rapid development and easier debugging in distributed systems.

Closing Thoughts

Minimal APIs enhance .NET application development by offering a lightweight, high-performance alternative to traditional MVC-based approaches. Whether you are an experienced developer or new to .NET software development, this pattern simplifies API creation while maintaining the flexibility and power of the .NET ecosystem.