2

Problem

I am currently building a helper for ASP.net MVC 3 and am running into a problem considering the UrlHelper.Action() method. Every request except for the first one (after the application start) the following code throws a NullReferenceException.

var src = htmlHelper.Url().Action("Css", "Asset", options);

Relevant Stack

System.Web.HttpServerVarsCollection.Get(String name) +8740566
   System.Web.Mvc.UrlRewriterHelper.WasThisRequestRewritten(HttpContextBase httpContext) +42
   System.Web.Mvc.UrlRewriterHelper.WasRequestRewritten(HttpContextBase httpContext) +23
   System.Web.Mvc.PathHelpers.GenerateClientUrlInternal(HttpContextBase httpContext, String contentPath) +163
   System.Web.Mvc.PathHelpers.GenerateClientUrl(HttpContextBase httpContext, String contentPath) +63
   System.Web.Mvc.UrlHelper.GenerateUrl(String routeName, String actionName, String controllerName, RouteValueDictionary routeValues, RouteCollection routeCollection, RequestContext requestContext, Boolean includeImplicitMvcValues) +150
   System.Web.Mvc.UrlHelper.Action(String actionName, String controllerName, Object routeValues) +55

Possible Cause

I use a lib called AttributeRouting which I installed through nuget and thought this might cause the problem but removing the reference has no effect.

Because it does work the first request but fails for every request after that I have a feeling it has something to do with code that runs at the application start but should run at request start or that certain variables/objects aren't persisted over the requests.

Extra Info

htmlHelper.Url() is the following extention method.

public static UrlHelper Url(this HtmlHelper helper)
{
    return new UrlHelper(helper.ViewContext.RequestContext);
}
Cœur
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Neothor
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  • I am having this same problem after upgrading to MVC3 - when all unit tests are run together, all of the tests where there is a call to UrlHelper fail. If I run them individually, or even by controller, they pass. Did you find a solution? – sydneyos Apr 24 '12 at 16:01

2 Answers2

0

var src = htmlHelper.Url().Action("Css", "Asset", options); Do you use that in a view or in one of your controllers?

Either way, both should have their own Url object defined (I made the assumption here that the htmlHelper object you use is one you created yourself).

public class MyController : Controller
{
    ....
    public ActionResult Index()
    {
        var src = Url.Action("Css", "Asset", options);
        ....
    }
}

or in your view:

<head>
    <meta charset="UTF-8">
    <title>@ViewBag.Title</title>
    @{
        var src = Url.Action("Css", "Asset", options);
    }
    <link rel="Stylesheet" href="@src" />

or better yet, just <link rel="Stylesheet" href="@Url.Action("Css","Asset",options)" />

Major Byte
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  • The helper I created is called from a view. The htmlHelper within the helper is passed to it when it is created by a extention method. – Neothor Aug 29 '11 at 07:58
  • Hmm, maybe I don't understand your question entirely then. Is there a need for rolling your own Url Helper instead of the one already available in the View? I mean, do you do more in the static you provided then just creating a new UrlHelper object? And where/when do you create your `htmlHelper` object? – Major Byte Aug 29 '11 at 09:23
0

Did you ever resolve this? I recently saw this error when I installed the IIS 7 Url Rewrite Module v.2.0. After uninstalling it the issue went away.

Greg Roberts
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