0Here, in this article we will learn ASP.NET Web API 2 action method return types.
A Web API 2 action method return types can be any of the following :
- Void
- HttpResponseMessage
- IHttpActionResult
- Other type or Complex type
Void
When an ASP.NET Web API return type is void, it will return an empty HTTP response.
In the following example a web API with void return:
Example
public class SampleController : ApiController{ public void Post() { }}Note: We are using fiddler to call Web API, it is a free web debugging proxy which logs all HTTP(s) traffic between your computer and the Internet
Result
Calling sample web API in fiddler
It is returning status code 204 No Content (an empty HTTP response)
HttpResponseMessage
- When Web API return type is HttpResponseMessage, Web API converts the return value directly into an HTTP response message.
- We can set the status code, content as per our requirement.
In the following example a web API with HttpResponseMessage return:
Example
public HttpResponseMessage Get(){ HttpResponseMessage response = Request.CreateResponse(HttpStatusCode.OK, "value1"); return response;}
Result
Calling sample Web API with HTTP GET request
In Response, It is returning status code 200 OK and Content
Note:Web API serialized model into the response body based on request header formatter
In the following example a web API return HttpResponseMessage with list of Countries in response body:
Example
public HttpResponseMessage Get(){ // list of Countries List Countries = new List(); Country country = new Country(); country.ID = 1; country.CountryName = "USA"; country.Capital = "Washington"; Countries.Add(country); //Countries to the response body. HttpResponseMessage response = Request.CreateResponse(HttpStatusCode.OK, Countries); return response;}
Result
In Response, It is returning status code 200 OK and Content
IHttpActionResult
IHttpActionResult is introduced in Web API 2, IHttpActionResult interface acts like a factory for HttpResponseMessage.
There are some advantages of using the IHttpActionResult over HttpResponseMessage
- The code is cleaner and easier to read
- Unit testing for controller action methods become easy
- It comes with custom built in responses
- Ok
- NotFound
- Exception
- Unauthorized
- BadRequest
- Conflict
- Redirect
In the following example a web API return IHttpActionResult with list of Countries in response body:
Example
public IHttpActionResult Get(int id){ // list of Countries List Countries = new List(); Country country = new Country(); country.ID = 1; country.CountryName = "USA"; country.Capital = "Washington"; Countries.Add(country); //finding country based on provided id var result = Countries.FirstOrDefault(x=> x.ID ==id); if (result == null) { //create a 404 (Not Found) response return NotFound(); } else { //creates a 200 (OK) response that contains the country return Ok(result); }}
Result
Calling sample web API with HTTP GET request and id
In Response, It is returning status code 200 OK and Content
Calling sample web API with HTTP GET request and id(which is not exist)
In Response, It is returning status code 404 Not Found
Other type or Complex type
- A Web API can return other or custom complex type
- Web API serialize value and return it into the response body
- The response status code 200 OK
- But in this approach we cannot directly return an error code, still we can throw an HttpResponseException for error codes
In the following example a web API with Complex return type:
Example
public class CountryController : ApiController{ public IEnumerable Get() { List Countries = new List(); Country country = new Country(); country.ID = 1; country.CountryName = "USA"; country.Capital = "Washington"; Countries.Add(country); return Countries; }}Result
Calling Country web API with HTTP GET request
In Response, It is returning status code 200 OK and Content
