HTTP Responses

ASP.NET Status Codes

• For a primer on HTTP status codes, check Frontend basics: Lecture 2

• There are multiple possible status codes for each action

• The ControllerBase the controllers should inherit from includes result methods for creating ActionResult objects

  • All ActionResult objects implement the IActionResult interface
  • Includes at least a status code, and can contain data such as view items or an error message
  • This result is processed into a response to then sent to client

Result methods

Status code example

[HttpGet("{id}")]
public IActionResult GetContactById(int id)
{
  // Contacts = list of contact objects, fetched from some repository
  var contact = Contacts.FirstOrDefault(c => c.Id == id);
  if (contact == null)
  {
    return NotFound();
  }
  return Ok(contact);
}

• The previous code first attempts to find a Contacts object using the ID provided in the URI parameter
  • If an item is not found, a 404 response is returned using NotFound()
    
  • Otherwise, the object is sent as a payload with a 200 OK code response using Ok(contact)