REST APIs with Web API

While this whole site is built with Razor Pages (server-rendered HTML), ASP.NET Core also lets you build pure JSON APIs — useful for mobile apps (like the .NET MAUI module), JavaScript front-ends, or other services.

Creating a minimal API controller

using Microsoft.AspNetCore.Mvc;

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

    public StudentsController(SchoolDbContext context)
    {
        _context = context;
    }

    [HttpGet]
    public async Task<ActionResult<List<Student>>> GetAll()
    {
        return await _context.Students.ToListAsync();
    }

    [HttpGet("{id}")]
    public async Task<ActionResult<Student>> GetById(int id)
    {
        var student = await _context.Students.FindAsync(id);
        if (student == null) return NotFound();
        return student;
    }

    [HttpPost]
    public async Task<ActionResult<Student>> Create(Student student)
    {
        _context.Students.Add(student);
        await _context.SaveChangesAsync();
        return CreatedAtAction(nameof(GetById), new { id = student.StudentId }, student);
    }

    [HttpPut("{id}")]
    public async Task<IActionResult> Update(int id, Student student)
    {
        if (id != student.StudentId) return BadRequest();
        _context.Entry(student).State = EntityState.Modified;
        await _context.SaveChangesAsync();
        return NoContent();
    }

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

        _context.Students.Remove(student);
        await _context.SaveChangesAsync();
        return NoContent();
    }
}

Registering controllers in Program.cs

builder.Services.AddControllers();
// ...
app.MapControllers();

REST verbs at a glance

Testing the API

Use the Swagger UI (enabled by default in new API projects at /swagger), or a tool like Postman, to call these endpoints without writing a client first.