Question

During development of an mvc web application, I’m encourtering issues running the local instance of the site. When I try to reload a page, after a successful first load, I’m seeing the below error. If I run the site through the VS virtual server, there are no issues. My app pool is running in integrated mode and it is running .net 4. Any idea why this is occurring? Is this enough information?

[NullReferenceException: Object reference not set to an instance of an object.]
System.Web.HttpServerVarsCollection.Get(String name) +109
System.Web.Mvc.UrlRewriterHelper.WasThisRequestRewritten(HttpContextBase httpContext) +59
System.Web.Mvc.PathHelpers.GenerateClientUrlInternal(HttpContextBase httpContext, String contentPath) +213
System.Web.Mvc.PathHelpers.GenerateClientUrlInternal(HttpContextBase httpContext, String contentPath) +168
System.Web.Mvc.PathHelpers.GenerateClientUrl(HttpContextBase httpContext, String contentPath) +148
LeadManager.Web.UI.Helpers.MenuHelper.GenerateUrl(String url) in C:\Development\Hg\LeadManager\Web.UI\Helpers\MenuHelper.cs:1132
LeadManager.Web.UI.Helpers.MenuHelper.BuildLeadManagementMenu(Menu navMenu, Agent agent) in C:\Development\Hg\LeadManager\Web.UI\Helpers\MenuHelper.cs:554
LeadManager.Web.UI.Helpers.MenuHelper.AddNavMenu(Agent agent) in C:\Development\Hg\LeadManager\Web.UI\Helpers\MenuHelper.cs:530
ASP._Page_Views_Shared__Layout_cshtml.Execute() in c:\Development\Hg\LeadManager\Web\Views\Shared_Layout.cshtml:115
System.Web.WebPages.WebPageBase.ExecutePageHierarchy() +279
System.Web.Mvc.WebViewPage.ExecutePageHierarchy() +103
System.Web.WebPages.WebPageBase.ExecutePageHierarchy(WebPageContext pageContext, TextWriter writer, WebPageRenderingBase startPage) +172
System.Web.WebPages.WebPageBase.Write(HelperResult result) +88
System.Web.WebPages.WebPageBase.RenderSurrounding(String partialViewName, Action1 body) +233
System.Web.WebPages.WebPageBase.PopContext() +233
System.Web.Mvc.ViewResultBase.ExecuteResult(ControllerContext context) +377
System.Web.Mvc.<>c__DisplayClass1c.<InvokeActionResultWithFilters>b__19() +32
System.Web.Mvc.ControllerActionInvoker.InvokeActionResultFilter(IResultFilter filter, ResultExecutingContext preContext, Func1 continuation) +748196
System.Web.Mvc.ControllerActionInvoker.InvokeActionResultFilter(IResultFilter filter, ResultExecutingContext preContext, Func1 continuation) +748196
System.Web.Mvc.ControllerActionInvoker.InvokeActionResultWithFilters(ControllerContext controllerContext, IList1 filters, ActionResult actionResult) +265
System.Web.Mvc.ControllerActionInvoker.InvokeAction(ControllerContext controllerContext, String actionName) +748160
System.Web.Mvc.Controller.ExecuteCore() +159
System.Web.Mvc.ControllerBase.Execute(RequestContext requestContext) +334
System.Web.Mvc.<>c_DisplayClassb.b_5() +62
System.Web.Mvc.Async.<>c_DisplayClass1.b_0() +15
System.Web.Mvc.<>c_DisplayClasse.b_d() +52
System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +437
System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +354

MenuHelper is used to build navigation menus. The code that fails is the return statement outside of the if:

private static string GenerateUrl(string url)
{
    if (instance == null)
    {
        // hack to enable using this on old web forms pages
        return UrlHelper.GenerateContentUrl(url, new HttpContextWrapper(HttpContext.Current));
    }
    return (new UrlHelper(instance.htmlHelper.ViewContext.RequestContext)).Content(url);
}

private static string GenerateUrl(string actionName, string controllerName)
{
    if (instance == null)
    {
        // hack to enable using this on old web forms pages
        return GenerateUrl(String.Format("{0}/{1}", controllerName, actionName));
    }

    if (instance.htmlHelper == null)
        throw new InvalidOperationException("htmlHelper has not been populated.");
    if (instance.htmlHelper.ViewContext == null)
        throw new InvalidOperationException("ViewContext has not been populated.");
    if (instance.htmlHelper.ViewContext.RequestContext == null)
        throw new InvalidOperationException("RequestContext has not been populated.");

    UrlHelper urlHelper = new UrlHelper(instance.htmlHelper.ViewContext.RequestContext);
    if (urlHelper == null)
        throw new InvalidOperationException("UrlHelper has not been populated.");

    if (String.IsNullOrEmpty(actionName))
        throw new InvalidOperationException("actionName has not been populated.");
    if (String.IsNullOrEmpty(controllerName))
        throw new InvalidOperationException("controllerName has not been populated.");

    return (urlHelper.Action(actionName, controllerName));
}

Answer 1

I found the issue, it was the IIS7 URL Rewrite Module. I’m not sure why or how but I solved the problem by uninstalling it.