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Lesson 6325 min read

Building a Web API

Bring everything together to build a complete, working REST API with ASP.NET Core and EF Core.

Putting It All Together

You now have every piece needed to build a real REST API: controllers, routing, model binding, EF Core, and dependency injection. This lesson combines them into one complete example.

DTOs (Data Transfer Objects)

A DTO is a class shaped specifically for what an API exposes — often different from your database entity, to avoid leaking internal fields or over-fetching data.

public class TaskDto
{
    [Required, StringLength(100)]
    public string Title { get; set; } = "";
    public bool IsComplete { get; set; }
}

A Complete API Controller

[ApiController]
[Route("api/[controller]")]
public class TasksController : ControllerBase
{
    private readonly AppDbContext context;


    public TasksController(AppDbContext context)
    {
        this.context = context;
    }


    [HttpGet]
    public async Task<IActionResult> GetAll()
    {
        var tasks = await context.Tasks.ToListAsync();
        return Ok(tasks);
    }


    [HttpGet("{id}")]
    public async Task<IActionResult> GetById(int id)
    {
        var task = await context.Tasks.FindAsync(id);
        if (task == null) return NotFound();
        return Ok(task);
    }


    [HttpPost]
    public async Task<IActionResult> Create(TaskDto dto)
    {
        var task = new TaskItem { Title = dto.Title, IsComplete = dto.IsComplete };
        context.Tasks.Add(task);
        await context.SaveChangesAsync();
        return CreatedAtAction(nameof(GetById), new { id = task.Id }, task);
    }


    [HttpDelete("{id}")]
    public async Task<IActionResult> Delete(int id)
    {
        var task = await context.Tasks.FindAsync(id);
        if (task == null) return NotFound();


        context.Tasks.Remove(task);
        await context.SaveChangesAsync();
        return NoContent();
    }
}

Testing with Swagger

ASP.NET Core Web API projects include Swagger (via Swashbuckle) by default in development — it generates an interactive documentation page where you can try every endpoint directly in the browser.

Try It Yourself

Run the app and navigate to /swagger — you'll see every endpoint in this controller listed, with a "Try it out" button for testing requests without needing a separate tool like Postman.

FAQs

For small apps and learning, yes. Larger production apps often add a "service layer" between controllers and DbContext to keep controllers thin — a natural next step once you're comfortable with the basics.

Summary

  • A complete API combines controllers, DTOs, EF Core, and DI.
  • DTOs decouple your API's public shape from your database entities.
  • Swagger provides interactive, auto-generated API documentation for testing.
Next Lesson →

API Authentication (JWT)