Application variable initialised in Controller constructor issue

Question

Using ASP.NET MVC3.

What I'm trying to do is initialize a Controller field/property with an Application state variable.

I.e. in my Application_Start() method I have

Application["stats"] = new Stats(); //this is fine

Accessing this via a Controller method, e.g.

public ActionResult Index()
{
  return View(HttpContext.Application["stats"]); //this is also fine
}

works fine too.

//blows up with a 'Object reference not set to an object' error.
private Stats stats;
public HomeController()
{
    stats= (Stats)(HttpContext.Application["stats"]);
}

Anyone able to explain what I'm failing to understand + how to go about fixing the problem ? If there's a better way, let me know (and just in case you're wondering, I'm not trying to load up application configuration or anything; just to keep live stats on the state of the website)

Thanks in advance

-Marcin

Darin Dimitrov · Accepted Answer · 2012-07-26 07:17:45Z

1

The HttpContext is not yet initialize inside a controller constructor and is null.

If you need to access any HttpContext related stuff this could be done at most early inside the Initialize method:

public class HomeController: Controller
{
    private Stats stats;

    protected override void Initialize(RequestContext requestContext)
    {
        base.Initialize(requestContext);
        stats = (Stats)(HttpContext.Application["stats"]);
    }
}

answered Jul 26, 2012 at 7:17

Darin Dimitrov

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1 Comment

Marcin Over a year ago

Genius ! Thanks heaps for that.

John Landheer · Accepted Answer · 2012-07-26 07:28:05Z

0

The HttpContext from your question is the property on the controller and as Darin said, that is not yet initialized. You can however use this:

private Stats stats;
public HomeController()
{
    stats= (Stats)(System.Web.HttpContext.Current.Application["stats"]);
}

answered Jul 26, 2012 at 7:28

John Landheer

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4 Comments

Darin Dimitrov Over a year ago

What about unit testing? HttpContext.Current kinda kills all hopes :-)

John Landheer Over a year ago

Absolutely, unit testing will be a "challenge". Your solution is much better than mine. I just wanted to point out that you could get to the HttpContext in the constructor.

Darin Dimitrov Over a year ago

HttpContext.Current is something that you really don't want to use. No matter the circumstances. There are always better ways.

Marcin Over a year ago

Thanks for that. Just trying to understand how unit testing would be easier using plain HttpContext rather than System.Web.HttpContext ? I found hanselman.com/blog/… which suggests that it's possible to mock it. So would the ability to mock be the only reason ? (Sorry, I've seen a few examples about mocking with Moq but haven't had a serious play with it).

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