Question

So I just implemented a base controller on my MVC3 site in order to have some things execute before every view is loaded. Particularly I wanted something that would act as a kind of master page code behind. Once I rolled this and made all my controllers inherit from my base controller I get this error:

Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. 

Exception Details: System.NullReferenceException: Object reference not set to an instance of an object.



[NullReferenceException: Object reference not set to an instance of an object.]
System.Web.Mvc.Controller.PossiblyLoadTempData() +11
System.Web.Mvc.Controller.ExecuteCore() +38
System.Web.Mvc.ControllerBase.Execute(RequestContext requestContext) +97
System.Web.Mvc.ControllerBase.System.Web.Mvc.IController.Execute(RequestContext requestContext) +10
System.Web.Mvc.<>c__DisplayClassb.<BeginProcessRequest>b__5() +37
System.Web.Mvc.Async.<>c__DisplayClass1.<MakeVoidDelegate>b__0() +21
System.Web.Mvc.Async.<>c__DisplayClass8`1.<BeginSynchronous>b__7(IAsyncResult _) +12
System.Web.Mvc.Async.WrappedAsyncResult`1.End() +62
System.Web.Mvc.<>c__DisplayClasse.<EndProcessRequest>b__d() +50
System.Web.Mvc.SecurityUtil.<GetCallInAppTrustThunk>b__0(Action f) +7
System.Web.Mvc.SecurityUtil.ProcessInApplicationTrust(Action action) +22
System.Web.Mvc.MvcHandler.EndProcessRequest(IAsyncResult asyncResult) +60
System.Web.Mvc.MvcHandler.System.Web.IHttpAsyncHandler.EndProcessRequest(IAsyncResult result) +9
System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +8970061
System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +184

I read a few places that you need to override CreateTempDataProvider() and return something or other, but I can’t quite figure out the code to do so. I am relatively new with .NET and have yet to override anything before, so I am not sure how to go about this. IF you have run into this before, or know what to do, please help!

Here is my base controller and the attempt at overriding that I have done so far to no avail:

 public class BaseController : Controller
{
    protected override void Initialize(System.Web.Routing.RequestContext requestContext)
    {

        string document = Path.Combine(HttpRuntime.AppDomainAppPath, "quote.xml");
        string _quote = "";
        string _author = "";
        XmlDocument xmlDoc = new XmlDocument();
        xmlDoc.Load(document);

        XmlNode Quote = xmlDoc.SelectSingleNode("quote/text");
        XmlNode Author = xmlDoc.SelectSingleNode("quote/author");

        _quote = Quote.InnerText;
        _author = Author.InnerText;

        ViewData["Quote"] = _quote;
    }

    protected override ITempDataProvider CreateTempDataProvider()
    {
        return base.CreateTempDataProvider();
    }
}

And here is the controller that is trying to run when I start debugging (dunno if you need it):

public class BlogController : BaseController
{
    private DarkRobotEntities1 db = new DarkRobotEntities1();

    //
    // GET: /Blog/

    public ViewResult Index()
    {
        var posts = db.Posts.Include(p => p.Blog).Include(p => p.Comments);
        return View(posts.ToList());
    }
...
}

Answer 1

You need to call base.Initialize() at the top of your overridden Initialize() method to initialize the base Controller class.

Otherwise, the properties used by PossiblyLoadTempData() will never be set.