Asp – Is it good practice to explicitly specify the type of ActionResult returned by a controller in ASP.NET MVC

asp.net-mvc

I've been using ASP.NET MVC for a little while now and seem to find myself constantly returning things other than ActionResult from my controllers. I obviously return ViewResults but also JSonResults and also a couple of custom results that we've built in house.

I'm wondering tho, if, instead of declaring my controller methods like:

public ActionResult Index()

I should start declaring them as

public ViewResult Index()

public JsonResult Search()

if I always know that the Index action on my controller will always return a ViewResult or the Search action on my controller will always return a JsonResult?

EDIT: Just to clarify, I'm talking specifically about situations where I will always want a specific type of ActionResult to be returned.

Best Answer

I vote yes for two reasons.

You are explicitly declaring what you expect the method to return and the compiler will catch any attempt to do otherwise. No need for a unit test that does a Assert( result is ViewResult).
You have to cast the result to the expected type in your tests when examining any properties unique to that result type (For example, checking Url property of the RedirectResult). Simply declaring the test variable as var removes any brittleness incurred by changing types.

Related Solutions

Asp.net-mvc – Can an ASP.NET MVC controller return an Image

Use the base controllers File method.

public ActionResult Image(string id)
{
    var dir = Server.MapPath("/Images");
    var path = Path.Combine(dir, id + ".jpg"); //validate the path for security or use other means to generate the path.
    return base.File(path, "image/jpeg");
}

As a note, this seems to be fairly efficient. I did a test where I requested the image through the controller (http://localhost/MyController/Image/MyImage) and through the direct URL (http://localhost/Images/MyImage.jpg) and the results were:

MVC: 7.6 milliseconds per photo
Direct: 6.7 milliseconds per photo

Note: this is the average time of a request. The average was calculated by making thousands of requests on the local machine, so the totals should not include network latency or bandwidth issues.

Json – ASP.NET MVC controller actions that return JSON or partial html

In your action method, return Json(object) to return JSON to your page.

public ActionResult SomeActionMethod() {
  return Json(new {foo="bar", baz="Blech"});
}

Then just call the action method using Ajax. You could use one of the helper methods from the ViewPage such as

<%= Ajax.ActionLink("SomeActionMethod", new AjaxOptions {OnSuccess="somemethod"}) %>

SomeMethod would be a javascript method that then evaluates the Json object returned.

If you want to return a plain string, you can just use the ContentResult:

public ActionResult SomeActionMethod() {
    return Content("hello world!");
}

ContentResult by default returns a text/plain as its contentType.
This is overloadable so you can also do:

return Content("<xml>This is poorly formatted xml.</xml>", "text/xml");

Best Answer

Related Solutions

Asp.net-mvc – Can an ASP.NET MVC controller return an Image

Json – ASP.NET MVC controller actions that return JSON or partial html

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