In Some cases I have NewtonSoft JSON.NET and in my controller I just return the Jobject from my controller and all is good.
But I have a case where I get some raw JS
sample example to return json data from web api GET method
[HttpGet] public IActionResult Get() { return Content("{\"firstName\": \"John\", \"lastName\": \"Doe\", \"lastUpdateTimeStamp\": \"2018-07-30T18:25:43.511Z\", \"nextUpdateTimeStamp\": \"2018-08-30T18:25:43.511Z\"); }