如何从ASP.NET Core Web API返回304结果?

我一直在从ASP.NET Core Web API中返回HTTP状态代码，如下所示:

I've been returning HTTP status codes from within my ASP.NET Core web api as follows:

// Return code 200:
return Controller.Ok(someOptionalMessageHere);

我现在需要返回状态码304(即未修改)，但是在"Microsoft.AspNetCore.Mvc.Controller"类中，从intellisense中看不到任何东西，这些名称空间也没有出现在在线API浏览器(?)中.正确的方法是什么?

I now have the need to return a status code 304 (i.e. not modified), but I don't see anything from intellisense in the "Microsoft.AspNetCore.Mvc.Controller" class that does that, nor do those namespaces appear in the online API browser (?). What is the proper way to do this?