Consider changing JsonResult's behavior when you provide a formatter

[rynowak]

This code is a bit of a trap.

            var formatter = new JsonOutputFormatter()
            {
                SerializerSettings = serializerSettings,
            };

            formatter.SupportedEncodings.Clear();
            formatter.SupportedEncodings.Add(encoding);

            return new JsonResult(content, formatter);

I new up a formatter, and give it the settings and and encoding a I want for this specific action, and then provide it to JsonResult. It will be ignored if I have a formatter registered in options that handles json (the default).

It turns out I have no way to specify a settings/formatter/encoding for a result ad-hoc unless I drop down to use objectresult.

[danroth27]

The explicitly specified formatter should always be used. The current behavior of using the specified formatter as a fallback from content negotiation is unexpected and incorrect.
If content negotiation fails and a formatter was not explicitly provided then the default JsonFormatter should be used.