Performing content negotiation

Content negotiation is theprocessby which the application returns data in a format that is requested by the client. This is usually done for API-style invocations, not requests that serve HTML. For example, a certain client might want data returned in JSON format, while others might prefer XML. ASP.NET Core supports this.

There are essentially two ways to achieve this:

• Through a route or query string parameter
• Through theAccept request header

The first approach lets you specify the format that you're interested in on the URL. Let's see how this works first:

1. Say you have the following action method:

public Model Process() { ... }

2. Let's forget whatModelactually is as it's just a POCO class that contains the properties you're interested in. It could be as simple as this:

public class Model
{
    public...