ASP.NET Core Web API Tutorials

Welcome to the comprehensive tutorials for building Web APIs with ASP.NET Core. This section will guide you through the essential concepts and practical implementation details to create robust and scalable APIs.

What is an ASP.NET Core Web API?

An ASP.NET Core Web API is a framework for building HTTP services that can be accessed by a broad range of clients, including browsers and mobile devices. It's built on top of ASP.NET Core, offering high performance, cross-platform compatibility, and a modern development experience.

Key Concepts

• HTTP Verbs: Understanding GET, POST, PUT, DELETE, and their usage in API design.
• Routing: How to define URL patterns to map incoming requests to specific actions.
• Controllers: The core components that handle incoming requests and return responses.
• Request and Response Handling: Processing data from requests and formatting data for responses.
• Data Formatting: Working with JSON and XML for data exchange.
• Model Binding and Validation: Automatically mapping incoming request data to C# objects and validating their content.
• Dependency Injection: Leveraging ASP.NET Core's built-in DI container for managing services.
• Asynchronous Programming: Writing efficient, non-blocking code for better performance.
• Authentication and Authorization: Securing your API endpoints.
• API Versioning: Strategies for managing different versions of your API.

Getting Started

Let's start by creating a simple Web API project.

1. Create a New Project

Open your terminal or command prompt and use the .NET CLI to create a new Web API project:

dotnet new webapi -o MyWebApiProject
cd MyWebApiProject

2. Understanding the Project Structure

The generated project includes:

• Program.cs: The entry point of your application.
• Controllers/: Directory for your API controllers.
• appsettings.json: Configuration file.
• launchSettings.json: Settings for running the application in different environments.

3. Creating Your First Controller

Inside the Controllers folder, create a new C# file named ProductsController.cs:

using Microsoft.AspNetCore.Mvc;
using System.Collections.Generic;
using MyWebApiProject.Models; // Assuming you have a Models folder

namespace MyWebApiProject.Controllers
{
    [ApiController]
    [Route("api/[controller]")] // Route: /api/products
    public class ProductsController : ControllerBase
    {
        private static List<Product> _products = new List<Product>
        {
            new Product { Id = 1, Name = "Laptop", Price = 1200.00M },
            new Product { Id = 2, Name = "Keyboard", Price = 75.00M },
            new Product { Id = 3, Name = "Mouse", Price = 25.00M }
        };

        // GET: api/products
        [HttpGet]
        public ActionResult<IEnumerable<Product>> Get()
        {
            return Ok(_products);
        }

        // GET: api/products/1
        [HttpGet("{id}", Name = "GetProduct")]
        public ActionResult<Product> Get(int id)
        {
            var product = _products.Find(p => p.Id == id);
            if (product == null)
            {
                return NotFound(); // Returns 404 Not Found
            }
            return Ok(product); // Returns 200 OK with product data
        }

        // POST: api/products
        [HttpPost]
        public ActionResult<Product> Post([FromBody] Product newProduct)
        {
            if (newProduct == null)
            {
                return BadRequest();
            }
            newProduct.Id = _products.Count > 0 ? _products.Max(p => p.Id) + 1 : 1;
            _products.Add(newProduct);
            // Return 201 Created and the location of the new resource
            return CreatedAtRoute("GetProduct", new { id = newProduct.Id }, newProduct);
        }
    }
}

You'll also need a Product model in a Models folder:

namespace MyWebApiProject.Models
{
    public class Product
    {
        public int Id { get; set; }
        public string Name { get; set; }
        public decimal Price { get; set; }
    }
}

4. Running the Application

In your terminal, run the application:

dotnet run

The output will show the URLs your API is listening on. You can then use tools like Postman or curl to test your endpoints.

Further Learning

Explore the following resources to deepen your understanding:

• Create a Web API with ASP.NET Core
• Web API Abstractions
• Web API Routing