Web api attribute routing, by content type, in dot net core 2?

Question

I'd like to be able to consume either posted JSON or form data at the same URL.

As things stand, I get:

fail: Microsoft.AspNetCore.Mvc.Internal.ActionSelector[1]
      Request matched multiple actions resulting in ambiguity. Matching actions: 
:
fail: Microsoft.AspNetCore.Server.Kestrel[13]
      Connection id "0HLDLB0LJCPJ4", Request id "0HLDLB0LJCPJ4:00000001": An unhandled exception was thrown by the application.
Microsoft.AspNetCore.Mvc.Internal.AmbiguousActionException: Multiple actions matched. The following actions matched route data and had all constraints satisfied:

https://andrewlock.net/model-binding-json-posts-in-asp-net-core/ suggests using different endpoints, but I can't do that in this case.

https://massivescale.com/web-api-routing-by-content-type/ suggests a way to do it for asp.net, for example:

[ContentTypeRoute("api/test/bytype", "application/json")]

or

[ContentTypeRoute("api/test/bytype", "application/x-www-form-urlencoded")]

but in .net core, we don't have System.Web.Http.Routing. Maybe it can be ported to use Microsoft.AspNetCore.Mvc.Routing... but is there something to replace IHttpRouteConstraint

My question: is something like this already built into .net core mvc?

For example, in Java's JAX-RS, there is @Consumes("application/json")

Answer 1

I accomplished this by the Consumes attribute:

http://example.com/payment/callback - Accepts x-www-form-urlencoded.

[HttpPost]
[Route("callback")]
[Consumes("application/x-www-form-urlencoded")]
public ActionResult Post([FromForm] string value)
{

}

http://example.com/payment/callback - Same url but accepts application/json.

[HttpPost]
[Route("callback")]
[Consumes("application/json")]
public ActionResult Post([FromBody] JObject value)
{

}