Swashbuckle/Swagger + ASP.Net Core: "Failed to load API definition"

Question

I develop an ASP.NET Core 2 application and included Swagger. Everything worked fine until I introduced a method without explicitly defining the HTTP action:

public class ErrorController : Controller
{
    [Route("/error")]
    public IActionResult Index()
    {
        return StatusCode(500, new Error("Internal error."));
    }
}

When I started the app with this method, the following message showed up:

Failed to load API definition.

Errors
Fetch error Internal Server Error /swagger/v1/swagger.json

As soon as I explicitly set e.g. [HttpGet] the error disappears. The problem with this is, I need this method to fire for all possible HTTP operations. Of course, I could specify all operations explicitly, but I have the feeling Swagger should be able to handle this correctly.

Why does Swagger behave this way?

Is there any configuration I can use?

Answer 1

Add Httpxxx([HttpGet], [HttpPost], ...) attribute for each Action method, or [ApiExplorerSettings(IgnoreApi = true)]