I cant show the API versions in response header with ApiVersioning .net Core - api

Question

I follow the instruction REST API versioning with ASP.NET Core to show My API version in the response header.
This is my Configuration code:
public void ConfigureServices(IServiceCollection services)
{
services.AddControllers();
services.AddMvc().AddNewtonsoftJson();
services.AddMvc(opt =>
{
services.AddRouting(env => env.LowercaseUrls = true);
services.AddApiVersioning(opt => {
opt.ApiVersionReader = new MediaTypeApiVersionReader();
opt.AssumeDefaultVersionWhenUnspecified = true;
opt.ReportApiVersions = true;
opt.DefaultApiVersion = new ApiVersion(1, 0);
opt.ApiVersionSelector = new CurrentImplementationApiVersionSelector(opt);
});
}
and this is my Controller :
[Route("/")]
[ApiVersion("1.0")]
public class RootController:Controller
{
[HttpGet(Name =nameof(GetRoot))]
public IActionResult GetRoot()
{
var response = new { href = Url.Link(nameof(GetRoot),null) };
return Ok(response);
}
}
when I test my API with postman I got this result :
I don't know why opt.ReportApiVersions = true; doesn't work.

Answer 1

The reason why it behaves this way is to disambiguate an API controller from a UI controller. In ASP.NET Core, there's not really any other built-in way to do so as - a controller is a controller.
There are a few other ways to change this behavior:
Opt out with options.UseApiBehavior = false as the was the case before [ApiController]
Add a custom IApiControllerSpecification that identifies an API controller (there's a built-in implementation that understands [ApiController])
Replace the default IApiControllerFilter service, which is really just an aggregation over all registered IApiControllerSpecification implementations
I hope that helps

Answer 2

I found the solution. I have to add [ApiController] to my Controller:
[Route("/")]
[ApiVersion("1.0")]
[ApiController]
public class RootController:Controller
{
[HttpGet(Name =nameof(GetRoot))]
public IActionResult GetRoot()
{
var response = new { href = Url.Link(nameof(GetRoot),null) };
return Ok(response);
}
}