How to Build RESTful APIs with ASP.NET Core

Learn how to build secure, scalable RESTful APIs using ASP.NET Core with this step-by-step guide for modern web development.

Digisoft

Jun 30, 2025 - 13:31

Jun 30, 2025 - 13:37

How to Build RESTful APIs with ASP.NET Core

In the digital age, where mobile apps, web apps, and cloud platforms need to communicate seamlessly, RESTful APIs have become the backbone of modern application architecture. A RESTful API allows different systems to interact using standard HTTP methods in a structured, stateless, and scalable manner.

When it comes to building robust, high-performance APIs, Microsoft’s ASP.NET Core framework stands out as a top choice. It’s a cross-platform, open-source solution that offers built-in support for routing, middleware, model binding, and seamless integration with databases. Whether you're developing internal tools or customer-facing platforms, ASP.NET Core provides the flexibility and scalability required for modern backend development.

If you're planning to develop a scalable API solution or modernize your architecture, it’s a smart decision to hire Dot NET developer with experience in ASP.NET Core. A skilled developer can help you leverage the full power of .NET to build secure, scalable, and maintainable APIs.

In this article, we’ll walk you through the complete process of building a RESTful API using ASP.NET Core — from project setup and database integration to endpoint implementation and best practices.

What is a RESTful API?

A RESTful API is based on REST (Representational State Transfer) architecture. It uses HTTP methods such as GET, POST, PUT, and DELETE to manage resources. Each resource is identified by a URI (Uniform Resource Identifier), and operations on them follow predictable patterns. REST APIs are stateless, meaning each request from a client must contain all the necessary information to process it.

Why Use ASP.NET Core for RESTful APIs?

ASP.NET Core is an open-source, cross-platform framework developed by Microsoft. It is well-suited for building APIs because:

It supports cross-platform development (Windows, macOS, Linux).
Offers high performance and scalability.
Has built-in features for dependency injection, model validation, and authentication.
Works seamlessly with Entity Framework Core for database operations.
Provides integrated support for Swagger/OpenAPI documentation.

Step-by-Step Guide to Building a RESTful API

1. Create a New ASP.NET Core Web API Project

Use the .NET CLI to scaffold your project:

This creates a basic template with a sample controller and setup.

2. Define Your Data Model

Let’s build a simple Product API. Start by creating a Product model in the Models folder:

3. Set Up the Database Context

Install Entity Framework Core packages:

Then, create a ProductContext:

4. Build the Products Controller

Create a ProductsController with basic CRUD operations:

csharp

[Route("api/[controller]")]
[ApiController]
public class ProductsController : ControllerBase
{
    private readonly ProductContext _context;

    public ProductsController(ProductContext context)
    {
        _context = context;
    }

    [HttpGet]
    public async Task>>> GetProducts() =>
        await _context.Products.ToListAsync();

    [HttpGet("{id}")]
    public async Task> GetProduct(int id)
    {
        var product = await _context.Products.FindAsync(id);
        if (product == null) return NotFound();
        return product;
    }

    [HttpPost]
    public async Task> PostProduct(Product product)
    {
        _context.Products.Add(product);
        await _context.SaveChangesAsync();
        return CreatedAtAction(nameof(GetProduct), new { id = product.Id }, product);
    }

    [HttpPut("{id}")]
    public async Task PutProduct(int id, Product product)
    {
        if (id != product.Id) return BadRequest();
        _context.Entry(product).State = EntityState.Modified;
        await _context.SaveChangesAsync();
        return NoContent();
    }

    [HttpDelete("{id}")]
    public async Task DeleteProduct(int id)
    {
        var product = await _context.Products.FindAsync(id);
        if (product == null) return NotFound();
        _context.Products.Remove(product);
        await _context.SaveChangesAsync();
        return NoContent();
    }
}

This controller enables your API to handle Create, Read, Update, and Delete operations for products.

5. Add Swagger for API Documentation

Swagger (OpenAPI) is useful for documenting and testing your API. Add it using:

In Program.cs:

Run your API and navigate to /swagger to access the documentation interface.

Best Practices for ASP.NET Core APIs

Use Data Transfer Objects (DTOs) to abstract internal models from the API response.
Implement versioning using route prefixes like /api/v1/products.
Handle exceptions using middleware or global exception filters.
Secure APIs with JWT authentication for protected endpoints.
Validate input data using model validation attributes like [Required], [StringLength].

Conclusion

Building RESTful APIs with ASP.NET Core is a powerful way to create scalable, maintainable, and secure backend services. Whether you're developing a simple CRUD API or a complex microservices architecture, ASP.NET Core offers the tools, performance, and flexibility needed to succeed.

If you're looking to outsource your next .NET project or need expert guidance, consider partnering with a professional Dot NET development company like Digisoft Solution, which specializes in building robust, scalable APIs tailored to your business needs.

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RESTful APIs using ASP.NET Core

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