https://github.com/microsoft/aspnet-api-versioning provides extension methods and types that allow endpoints within an Asp.Net Core web host to be selected based on version numbers provided either through headers or through the URL route. It acknowledges however that versioning by custom media types is not supported.
This repository shows an implementation of MatcherPolicy for Asp.Net Core that discriminates
endpoints based on the Content-Type defined in the HTTP header and thus custom content types,
making it then possible to have two endpoints with identical URLs and HTTP-methods, but to be
differentiated by content type.
This is a work in progress.