Question

Just wondering why almost every controller method I see in sample MVC code returns ActionResult, even if it’s obvious that the code can only return one type of result. I understand there are certain instances where it’s warranted because you may return, say a RedirectResult or a ViewResult depending on the logic, but that’s not the case for most of the methods I’ve seen.

Isn’t it tantamount to having a return type of ‘object’ on a method? Why not just specify JsonResult, or FileResult or ViewResult as the return type? Is there a benefit I’m not seeing to settting the return type to ActionResult on every controller method?

Classic example:

public ActionResult Index()
{
    return View();
}

Why does this seem to be the norm instead of this:

public ViewResult Index()
{
    return View();
}

EDIT: So far all of the responses except for one have indicated that ActionResult is just more generic. I know that much. 🙂 Why is this accepted practice on a controller method though, and not anywhere else? You don’t just return the highest level-base classes of a type that you can on a normal method, you attempt to return the most specific type you can usually. What makes controller methods so different that bloggers and “sample code writers” (yes, I made that term up) would just resort to returning ActionResult?

Answer 1

quoted verbatim from an accepted answer here on SO. makes sense to me:

Must ASP.NET MVC Controller Methods Return ActionResult?

You can absolutely use specific return
types, even though most examples on
the web seems to return the
ActionResult. The only time I would
return the ActionResult class is when
different paths of the action method
returns different subtypes.

Steven Sanderson also recommends
returning specific types in his book
Pro ASP.NET MVC Framework. Take a look
at the quote below:

“This action method specifically
declares that it returns an instance
of ViewResult. It would work just the
same if instead the method return type
was ActionResult (the base class for
all action results). In fact, some
ASP.NET MVC programmers declare all
their action methods as returning a
nonspecific ActionResult, even if they
know for sure that it will always
return one particular subclass.
However, it’s a well-established
principle in object-oriented
programming that methods should return
the most specific type they can (as
well as accepting the most general
parameter types they can). Following
this principle maximizes convenience
and flexibility for code that calls
your method, such as your unit tests.“

see also:

http://www.bengtbe.com/blog/post/2009/07/01/Use-specific-return-types-in-your-ASPNET-MVC-action-methods.aspx