Web API Development

65 min

ASP.NET Core Web API is a framework for building HTTP services that can be accessed from any client (web browsers, mobile apps, desktop applications, IoT devices). Web APIs enable you to expose application functionality over HTTP, making it accessible to diverse clients. APIs are essential for modern applications that need to support multiple client types. Understanding Web API enables building service-oriented architectures. Web APIs are the foundation of modern web applications.

Web APIs provide a robust, scalable way to build RESTful APIs following REST principles (resource-based URLs, HTTP methods, stateless communication). REST APIs use standard HTTP methods (GET, POST, PUT, DELETE) to perform operations on resources. REST principles enable APIs that are intuitive, cacheable, and scalable. Understanding REST enables building effective APIs. REST is the dominant API style.

Web APIs can return JSON, XML, or other formats and support content negotiation, allowing clients to request their preferred format. Content negotiation enables APIs to serve different clients with different format requirements. JSON is the most common format for modern APIs. Understanding content negotiation enables flexible APIs. Content negotiation improves API usability.

API controllers inherit from ControllerBase (not Controller) and use attributes like [ApiController] and [Route] for configuration. [ApiController] enables automatic model validation, binding source inference, and standardized error responses. Controllers return ActionResult<T> or IActionResult for flexible responses. Understanding API controllers enables building RESTful endpoints. API controllers are simpler than MVC controllers.

HTTP status codes communicate request results: 200 (OK), 201 (Created), 400 (Bad Request), 404 (Not Found), 500 (Server Error). Proper status codes enable clients to understand API responses. Understanding status codes enables building clear APIs. Status codes are essential for API usability.

Best practices include using proper HTTP methods, returning appropriate status codes, implementing versioning for API evolution, documenting APIs (Swagger/OpenAPI), and handling errors consistently. Understanding Web API development enables building production-ready APIs. Web APIs are essential for modern application architecture.

Key Concepts

ASP.NET Core Web API builds HTTP services accessible from any client.
Web APIs provide a robust way to build RESTful APIs.
Web APIs support JSON, XML, and content negotiation.
API controllers use [ApiController] and [Route] attributes.
Proper HTTP methods and status codes are essential.

Learning Objectives

Master

Creating Web API controllers and endpoints
Building RESTful APIs following REST principles
Implementing content negotiation
Using proper HTTP methods and status codes

Develop

Understanding RESTful API design
Designing scalable API architectures
Appreciating Web API's role in modern applications

Tips

Use [ApiController] attribute for automatic validation and error handling.
Return appropriate HTTP status codes for different scenarios.
Use proper HTTP methods (GET for retrieval, POST for creation, etc.).
Document APIs with Swagger/OpenAPI for better developer experience.

Common Pitfalls

Not using proper HTTP methods, causing confusion.
Not returning appropriate status codes, making error handling difficult.
Not implementing API versioning, breaking clients when evolving.
Not documenting APIs, making integration difficult.

Summary

ASP.NET Core Web API builds HTTP services for diverse clients.
Web APIs provide robust RESTful API development.
Content negotiation enables flexible format support.
Understanding Web API enables modern application development.
Web APIs are essential for service-oriented architectures.

Exercise

Create a RESTful API for managing products.

[ApiController]
[Route("api/[controller]")]
public class ProductsController : ControllerBase
{
    private readonly ApplicationDbContext _context;
    
    public ProductsController(ApplicationDbContext context)
    {
        _context = context;
    }
    
    [HttpGet]
    public async Task<ActionResult<IEnumerable<Product>>> GetProducts()
    {
        return await _context.Products.ToListAsync();
    }
    
    [HttpGet("{id}")]
    public async Task<ActionResult<Product>> GetProduct(int id)
    {
        var product = await _context.Products.FindAsync(id);
        if (product == null)
            return NotFound();
        return product;
    }
}

Web API Development