Controller方法返回ActionResult的原因是什么？ （ASP.NET Core Web API）

Question

I'm pretty new to Web APIs. I observed that some methods return an ActionResult . Why is that? Isn't it enough returning, for example, a CustomerDto instead?

Returning ActionResult gives no clue about the actual object being returned. Do I miss something?

Answer 1

There are multiple ways of designing your Web API. You can return CustomerDto, in your case. According to the documentation ( https://docs.microsoft.com/en-us/aspnet/web-api/overview/getting-started-with-aspnet-web-api/action-results ), a Web API controller action can return any of the following: - void - HttpResponseMessage - IHttpActionResult - Some other type

By using IHttpActionResult, you can better control the Http Reponse code.

Answer 2

Web API is a flexible platform - you can write simple APIs that always just return particular result types (such as your CustomerDto ) or you can write more complex APIs that really do care about HTTP semantics and want to have more control over status codes, other HTTP headers, etc.

Or maybe your method is dealing with "resources" which have more complex representations that aren't easily modelled by a single DTO class in C#, and so you want the flexibility of multiple possible "return types".

If you don't want that level of control, yes, you can carry on and just return your DTO types. Nobody is (to the best of my knowledge) forcing you to use ActionResult instead.

Answer 3

In ASP.NET Core the former MVC "Controller"-class and Web Api "ApiController"-class where merged together to one "Controller"-class. The ActionResult method, which is a classic MVC method and useful when building an MVC application, where also included in that merged and that's why it's being available when also building a Web Api.

Answer 4

If you notice the prebuild project of the .net core web api, not all functions return ActionResult or IActionResult . So yes, you can totally return something like CustomerDto . This way you can return an object as json, with the status code 200. However let's say your action is taking in some input and you are not always sure if there will be a valid output. In this case you will want to return status code 200 only if successful, 400 (badRequest) if the user sent invalid data or any other status code. This is the standard way of handling http requests.

So, by using IActionResult you can either return a CustomerDto object by using return Json(customer) or return Ok(customer) , or you can return use BadRequest(myErrors) when you run into errors.