Can a controller completely replace what the http handler does?

Question

I want to know if the controller can completely replace the http handler when there was no view. The function looks similar.

Answer 1

Of course:

public ActionResult Index()
{
    return Content("No view involved here", "text/plain");
}

or

public ActionResult Index()
{
    return File("test.pdf", "application/pdf");
}

or

public ActionResult Index()
{
    return Json(new { foo = "bar" });
}

In all of these examples, there is no representation. The controller acts as an HTTP handler.