ASP.NET Core does support out of the box JSON, XML, or plain text formatters based on the ACCEPT Header. In this post, I’ll explain how to specify other formatters and return them based on the ACCEPT Header. As an example, I use a CSV formatter to return a CSV formatter. A controller method returns the format based on the ACCEPT Header which is specified by the client. This can be very useful in cases where you need to export your data to Excel, and the use of more formats makes your application more accessible.
ASP.NET Core Web API custom formatters
Use accept headers to return new formats like CSV from an ASP.NET Core Rest service