Controllers

Controllers in a web API are classes that derive from ControllerBase. Controllers are activated and disposed on a per request basis.

ControllerBase class

A controller-based web API consists of one or more controller classes that derive from ControllerBase. The web API project template provides a starter controller:

[ApiController]
[Route("[controller]")]
public class WeatherForecastController : ControllerBase

Web API controllers should typically derive from ControllerBase rather than from Controller. Controller derives from ControllerBase and adds support for views, so it's for handling web pages, not web API requests.

The ControllerBase class provides many properties and methods that are useful for handling HTTP requests. For example, CreatedAtAction returns a 201 status code:

[HttpPost]
[ProducesResponseType(StatusCodes.Status201Created)]
[ProducesResponseType(StatusCodes.Status400BadRequest)]
public ActionResult<Pet> Create(Pet pet)
{
    pet.Id = _petsInMemoryStore.Any() ?
             _petsInMemoryStore.Max(p => p.Id) + 1 : 1;
    _petsInMemoryStore.Add(pet);

    return CreatedAtAction(nameof(GetById), new { id = pet.Id }, pet);
}

ApiController attribute

The [ApiController] attribute can be applied to a controller class to enable the following opinionated, API-specific behaviors:

• Attribute routing requirement
• Automatic HTTP 400 responses
• Binding source parameter inference
• Multipart/form-data request inference
• Problem details for error status codes

Example:

[ApiController]
[Route("[controller]")]
public class WeatherForecastController : ControllerBase