object reference not set to an instance of an object happens after cache reset

Jack Gill 7 posts 77 karma points

Apr 14, 2016 @ 15:43

Object reference not set to an instance of an object - Happens after cache reset

Hey,

I'm getting this error on my site:

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

Line 38:     else

Line 39:     {

Line 40:        @Html.Action("GetTTForm", "Membership", new { currentNodeId = Model.Id, currentUrl = library.NiceUrl(Model.Id), formAction = Model.FormAction })

Line 41:    }

On the member login page of the site, but it only seems to appear after the macro cache time is up which is currently an hour. If I delete my AppData folder and swap it with another version of my AppData folder and then republish the entire site - the problem page will work again for the next hour.

I'm no where near an expert in umbraco, but I am finding this a very vague error - the controller it is referencing hasn't changed (to be clear this page on the site worked up with no problems until recently) and none of the ID's / Variables it operates have also changed.

Is it at all possible it could be an IIS issue causing a crash when the cache is renewed?

Any help would be fantastic as this has plagued me for all this week!

Thanks,

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Nicholas Westby 2054 posts 7104 karma points c-trib

Apr 14, 2016 @ 16:18

Is there a stack trace to go along with the error message? There usually is in the Umbraco log file. Also, which version of Umbraco are you using?

You might try splitting that line into a few different lines to help narrow down the issue. For example, perhaps Model is null sometimes for some reason. If you put the error on a different line (var modelId = Model.Id;), then you might get some info about the particular member access attempt that is causing the error.

You could also try logging some variables to see if that helps narrow down the issue. That works like this: LogHelper.Info<SomeClass>("Some message.");

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Jack Gill 7 posts 77 karma points

Apr 14, 2016 @ 16:27

Thanks Nicholas,

here is the stack trace to go with it:

[NullReferenceException: Object reference not set to an instance of an object.]
   site.co.uk.logic.Controllers.MembershipController.GetTTForm(Int32 currentNodeId, String currentUrl, EnMyTTAction formAction) in path~\Controllers\MembershipController.cs:324
   lambda_method(Closure , ControllerBase , Object[] ) +247
   System.Web.Mvc.ReflectedActionDescriptor.Execute(ControllerContext controllerContext, IDictionary`2 parameters) +280
   System.Web.Mvc.ControllerActionInvoker.InvokeActionMethod(ControllerContext controllerContext, ActionDescriptor actionDescriptor, IDictionary`2 parameters) +35
   System.Web.Mvc.Async.<>c__DisplayClass42.<BeginInvokeSynchronousActionMethod>b__41() +33
   System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeActionMethod(IAsyncResult asyncResult) +42
   System.Web.Mvc.Async.<>c__DisplayClass39.<BeginInvokeActionMethodWithFilters>b__33() +80
   System.Web.Mvc.Async.<>c__DisplayClass4f.<InvokeActionMethodFilterAsynchronously>b__49() +386
   System.Web.Mvc.Async.<>c__DisplayClass4f.<InvokeActionMethodFilterAsynchronously>b__49() +386
   System.Web.Mvc.Async.<>c__DisplayClass4f.<InvokeActionMethodFilterAsynchronously>b__49() +386
   System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeActionMethodWithFilters(IAsyncResult asyncResult) +42
   System.Web.Mvc.Async.<>c__DisplayClass2a.<BeginInvokeAction>b__20() +32
   System.Web.Mvc.Async.<>c__DisplayClass25.<BeginInvokeAction>b__22(IAsyncResult asyncResult) +185
   System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeAction(IAsyncResult asyncResult) +38
   System.Web.Mvc.<>c__DisplayClass1d.<BeginExecuteCore>b__18(IAsyncResult asyncResult) +27
   System.Web.Mvc.Async.<>c__DisplayClass4.<MakeVoidDelegate>b__3(IAsyncResult ar) +22
   System.Web.Mvc.Controller.EndExecuteCore(IAsyncResult asyncResult) +53
   System.Web.Mvc.Async.<>c__DisplayClass4.<MakeVoidDelegate>b__3(IAsyncResult ar) +22
   System.Web.Mvc.Controller.EndExecute(IAsyncResult asyncResult) +38
   System.Web.Mvc.<>c__DisplayClass8.<BeginProcessRequest>b__3(IAsyncResult asyncResult) +42
   System.Web.Mvc.Async.<>c__DisplayClass4.<MakeVoidDelegate>b__3(IAsyncResult ar) +22
   System.Web.Mvc.MvcHandler.EndProcessRequest(IAsyncResult asyncResult) +38
   System.Web.Mvc.<>c__DisplayClass4.<Wrap>b__3() +15
   System.Web.Mvc.ServerExecuteHttpHandlerWrapper.Wrap(Func`1 func) +27
   System.Web.HttpServerUtility.ExecuteInternal(IHttpHandler handler, TextWriter writer, Boolean preserveForm, Boolean setPreviousPage, VirtualPath path, VirtualPath filePath, String physPath, Exception error, String queryStringOverride) +1737

[HttpException (0x80004005): Error executing child request for handler 'System.Web.Mvc.HttpHandlerUtil+ServerExecuteHttpHandlerAsyncWrapper'.]
   System.Web.HttpServerUtility.ExecuteInternal(IHttpHandler handler, TextWriter writer, Boolean preserveForm, Boolean setPreviousPage, VirtualPath path, VirtualPath filePath, String physPath, Exception error, String queryStringOverride) +2408
   System.Web.HttpServerUtility.Execute(IHttpHandler handler, TextWriter writer, Boolean preserveForm, Boolean setPreviousPage) +131
   System.Web.HttpServerUtility.Execute(IHttpHandler handler, TextWriter writer, Boolean preserveForm) +36
   System.Web.Mvc.Html.ChildActionExtensions.ActionHelper(HtmlHelper htmlHelper, String actionName, String controllerName, RouteValueDictionary routeValues, TextWriter textWriter) +595
   System.Web.Mvc.Html.ChildActionExtensions.Action(HtmlHelper htmlHelper, String actionName, String controllerName, RouteValueDictionary routeValues) +114
   ASP._Page_Views_MyTTPage_cshtml.Execute() in c:\inetpub\wwwroot\New folder\Views\MyTTPage.cshtml:40
   System.Web.WebPages.WebPageBase.ExecutePageHierarchy() +253
   System.Web.Mvc.WebViewPage.ExecutePageHierarchy() +147
   System.Web.WebPages.WebPageBase.ExecutePageHierarchy(WebPageContext pageContext, TextWriter writer, WebPageRenderingBase startPage) +107
   Umbraco.Core.Profiling.ProfilingView.Render(ViewContext viewContext, TextWriter writer) +232
   System.Web.Mvc.ViewResultBase.ExecuteResult(ControllerContext context) +375
   System.Web.Mvc.<>c__DisplayClass1a.<InvokeActionResultWithFilters>b__17() +31
   System.Web.Mvc.ControllerActionInvoker.InvokeActionResultFilter(IResultFilter filter, ResultExecutingContext preContext, Func`1 continuation) +437
   System.Web.Mvc.ControllerActionInvoker.InvokeActionResultFilter(IResultFilter filter, ResultExecutingContext preContext, Func`1 continuation) +437
   System.Web.Mvc.Async.<>c__DisplayClass25.<BeginInvokeAction>b__22(IAsyncResult asyncResult) +185
   System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeAction(IAsyncResult asyncResult) +38
   System.Web.Mvc.<>c__DisplayClass1d.<BeginExecuteCore>b__18(IAsyncResult asyncResult) +27
   System.Web.Mvc.Async.<>c__DisplayClass4.<MakeVoidDelegate>b__3(IAsyncResult ar) +22
   System.Web.Mvc.Controller.EndExecuteCore(IAsyncResult asyncResult) +53
   System.Web.Mvc.Async.<>c__DisplayClass4.<MakeVoidDelegate>b__3(IAsyncResult ar) +22
   System.Web.Mvc.Controller.EndExecute(IAsyncResult asyncResult) +38
   System.Web.Mvc.<>c__DisplayClass8.<BeginProcessRequest>b__3(IAsyncResult asyncResult) +42
   System.Web.Mvc.Async.<>c__DisplayClass4.<MakeVoidDelegate>b__3(IAsyncResult ar) +22
   System.Web.Mvc.MvcHandler.EndProcessRequest(IAsyncResult asyncResult) +38
   System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +399
   System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +137

I'll take a look at your other suggestions in the mean time,

Thanks.

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Nicholas Westby 2054 posts 7104 karma points c-trib

Apr 14, 2016 @ 16:35

What does line 324 of MemberShipController look like?:

   site.co.uk.logic.Controllers.MembershipController.GetTTForm(Int32 currentNodeId, String currentUrl, EnMyTTAction formAction) in path~\Controllers\MembershipController.cs:324

Based on this part of the stack trace, that's where the error is.

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Jack Gill 7 posts 77 karma points

Apr 14, 2016 @ 17:16

Line 321:      catch (Exception ex)
Line 322:      {
Line 323:           Log.Error("Error getting My TT form", ex);
Line 324:           throw;
Line 325:      }

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Nicholas Westby 2054 posts 7104 karma points c-trib

Apr 14, 2016 @ 17:32

Try removing that try/catch block. It seems to be preventing the stack trace from showing the true source of the exception.

Alternatively, if you use LogHelper.Error<MembershipController>("Error getting My TT form", ex);, that should show the true stack trace to help you narrow down the error.

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Jack Gill 7 posts 77 karma points

Apr 14, 2016 @ 19:42

Ok, I removed the catch and getting the same error - but the stack trace now looks like this:

[NullReferenceException: Object reference not set to an instance of an object.]
   site.co.uk.logic.Controllers.MembershipController.GetMyTTForm(Int32 currentNodeId, String currentUrl, EnMyTTAction formAction) in path~\Controllers\MembershipController.cs:272
   lambda_method(Closure , ControllerBase , Object[] ) +246
   System.Web.Mvc.ReflectedActionDescriptor.Execute(ControllerContext controllerContext, IDictionary`2 parameters) +279
   System.Web.Mvc.ControllerActionInvoker.InvokeActionMethod(ControllerContext controllerContext, ActionDescriptor actionDescriptor, IDictionary`2 parameters) +34
   System.Web.Mvc.Async.<>c__DisplayClass42.<BeginInvokeSynchronousActionMethod>b__41() +32
   System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeActionMethod(IAsyncResult asyncResult) +41
   System.Web.Mvc.Async.<>c__DisplayClass39.<BeginInvokeActionMethodWithFilters>b__33() +79
   System.Web.Mvc.Async.<>c__DisplayClass4f.<InvokeActionMethodFilterAsynchronously>b__49() +386
   System.Web.Mvc.Async.<>c__DisplayClass4f.<InvokeActionMethodFilterAsynchronously>b__49() +386
   System.Web.Mvc.Async.<>c__DisplayClass4f.<InvokeActionMethodFilterAsynchronously>b__49() +386
   System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeActionMethodWithFilters(IAsyncResult asyncResult) +42
   System.Web.Mvc.Async.<>c__DisplayClass2a.<BeginInvokeAction>b__20() +32
   System.Web.Mvc.Async.<>c__DisplayClass25.<BeginInvokeAction>b__22(IAsyncResult asyncResult) +185
   System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeAction(IAsyncResult asyncResult) +38
   System.Web.Mvc.<>c__DisplayClass1d.<BeginExecuteCore>b__18(IAsyncResult asyncResult) +27
   System.Web.Mvc.Async.<>c__DisplayClass4.<MakeVoidDelegate>b__3(IAsyncResult ar) +22
   System.Web.Mvc.Controller.EndExecuteCore(IAsyncResult asyncResult) +53
   System.Web.Mvc.Async.<>c__DisplayClass4.<MakeVoidDelegate>b__3(IAsyncResult ar) +22
   System.Web.Mvc.Controller.EndExecute(IAsyncResult asyncResult) +38
   System.Web.Mvc.<>c__DisplayClass8.<BeginProcessRequest>b__3(IAsyncResult asyncResult) +42
   System.Web.Mvc.Async.<>c__DisplayClass4.<MakeVoidDelegate>b__3(IAsyncResult ar) +22
   System.Web.Mvc.MvcHandler.EndProcessRequest(IAsyncResult asyncResult) +38
   System.Web.Mvc.<>c__DisplayClass4.<Wrap>b__3() +15
   System.Web.Mvc.ServerExecuteHttpHandlerWrapper.Wrap(Func`1 func) +27
   System.Web.HttpServerUtility.ExecuteInternal(IHttpHandler handler, TextWriter writer, Boolean preserveForm, Boolean setPreviousPage, VirtualPath path, VirtualPath filePath, String physPath, Exception error, String queryStringOverride) +1737

[HttpException (0x80004005): Error executing child request for handler 'System.Web.Mvc.HttpHandlerUtil+ServerExecuteHttpHandlerAsyncWrapper'.]
   System.Web.HttpServerUtility.ExecuteInternal(IHttpHandler handler, TextWriter writer, Boolean preserveForm, Boolean setPreviousPage, VirtualPath path, VirtualPath filePath, String physPath, Exception error, String queryStringOverride) +2408
   System.Web.HttpServerUtility.Execute(IHttpHandler handler, TextWriter writer, Boolean preserveForm, Boolean setPreviousPage) +131
   System.Web.HttpServerUtility.Execute(IHttpHandler handler, TextWriter writer, Boolean preserveForm) +36
   System.Web.Mvc.Html.ChildActionExtensions.ActionHelper(HtmlHelper htmlHelper, String actionName, String controllerName, RouteValueDictionary routeValues, TextWriter textWriter) +595
   System.Web.Mvc.Html.ChildActionExtensions.Action(HtmlHelper htmlHelper, String actionName, String controllerName, RouteValueDictionary routeValues) +114
   ASP._Page_Views_MyTTPage_cshtml.Execute() in c:\inetpub\wwwroot\New folder\Views\MyTTPage.cshtml:40
   System.Web.WebPages.WebPageBase.ExecutePageHierarchy() +253
   System.Web.Mvc.WebViewPage.ExecutePageHierarchy() +147
   System.Web.WebPages.WebPageBase.ExecutePageHierarchy(WebPageContext pageContext, TextWriter writer, WebPageRenderingBase startPage) +107
   Umbraco.Core.Profiling.ProfilingView.Render(ViewContext viewContext, TextWriter writer) +232
   System.Web.Mvc.ViewResultBase.ExecuteResult(ControllerContext context) +375
   System.Web.Mvc.<>c__DisplayClass1a.<InvokeActionResultWithFilters>b__17() +31
   System.Web.Mvc.ControllerActionInvoker.InvokeActionResultFilter(IResultFilter filter, ResultExecutingContext preContext, Func`1 continuation) +437
   System.Web.Mvc.ControllerActionInvoker.InvokeActionResultFilter(IResultFilter filter, ResultExecutingContext preContext, Func`1 continuation) +437
   System.Web.Mvc.Async.<>c__DisplayClass25.<BeginInvokeAction>b__22(IAsyncResult asyncResult) +185
   System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeAction(IAsyncResult asyncResult) +38
   System.Web.Mvc.<>c__DisplayClass1d.<BeginExecuteCore>b__18(IAsyncResult asyncResult) +27
   System.Web.Mvc.Async.<>c__DisplayClass4.<MakeVoidDelegate>b__3(IAsyncResult ar) +22
   System.Web.Mvc.Controller.EndExecuteCore(IAsyncResult asyncResult) +53
   System.Web.Mvc.Async.<>c__DisplayClass4.<MakeVoidDelegate>b__3(IAsyncResult ar) +22
   System.Web.Mvc.Controller.EndExecute(IAsyncResult asyncResult) +38
   System.Web.Mvc.<>c__DisplayClass8.<BeginProcessRequest>b__3(IAsyncResult asyncResult) +42
   System.Web.Mvc.Async.<>c__DisplayClass4.<MakeVoidDelegate>b__3(IAsyncResult ar) +22
   System.Web.Mvc.MvcHandler.EndProcessRequest(IAsyncResult asyncResult) +38
   System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +399
   System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +137

Line 272 is refering to this:

    public ActionResult GetMyTTForm(int currentNodeId, string currentUrl, Enums.EnMyTTAction formAction)
            {
                    var myTTPage = new CacheController().GetCachedMyTTPage(currentNodeId);

 Line 272:                   var model = new MembershipViewModel()
                    {
                        LoginPageUrl =
                            string.Format("{0}?{1}={2}", currentUrl, domain.Constants.QueryString.ACTION,
                                Enums.EnMyTTAction.Login)
                        ,
                        RegisterPageUrl =
                            string.Format("{0}?{1}={2}", currentUrl, domain.Constants.QueryString.ACTION,
                                Enums.EnMyTTAction.Register)
                        ,
                        ForgottenPasswordPageUrl =
                            string.Format("{0}?{1}={2}", currentUrl, domain.Constants.QueryString.ACTION,
                                Enums.EnMyTTAction.ForgottenPassword)
                        ,
                        VisitorType = Session.GetVisitor().VisitorType
                        ,
                        LoginIntroductoryText = myTTPage.MyTTPageLoginIntroductoryText
                        ,
                        RegisterIntroductoryText = myTTPage.MyTTPageRegisterIntroductoryText
                        ,
                        ImageUrl = myTTPage.MyTTPageMainImage.Url
                    };

                    switch (formAction)
                    {
                        case Enums.EnMyTTAction.Login:
                            return View("~/Views/Partials/Membership/Login/_LoginForm.cshtml", model);

                        case Enums.EnMyTTAction.Register:
                            return View("~/Views/Partials/Membership/Register/_RegisterForm.cshtml", model);

                        case Enums.EnMyTTAction.ForgottenPassword:
                            return View("~/Views/Partials/Membership/ForgottenPassword/_ForgottenPasswordForm.cshtml", model);

                        case Enums.EnMyTTAction.ValidatePasswordResetCode:
                            return ValidatePasswordResetCode(currentNodeId, currentUrl, Request.QueryString[domain.Constants.QueryString.CODE]);

                        case Enums.EnMyTTAction.ResetPassword:
                            return View("~/Views/Partials/Membership/ResetPassword/_ResetPasswordForm.cshtml", model);

                        case Enums.EnMyTTAction.AuthenticatedResetPassword:
                            return AuthenticatedPasswordReset(currentNodeId, currentUrl);

                        default:
                            throw new NotImplementedException(formAction.ToString());
                    }
            }

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Nicholas Westby 2054 posts 7104 karma points c-trib

Apr 14, 2016 @ 19:48

Sounds like the error is somewhere in here (since this is all one line of code):

                    var model = new MembershipViewModel()
                    {
                        LoginPageUrl =
                            string.Format("{0}?{1}={2}", currentUrl, domain.Constants.QueryString.ACTION,
                                Enums.EnMyTTAction.Login)
                        ,
                        RegisterPageUrl =
                            string.Format("{0}?{1}={2}", currentUrl, domain.Constants.QueryString.ACTION,
                                Enums.EnMyTTAction.Register)
                        ,
                        ForgottenPasswordPageUrl =
                            string.Format("{0}?{1}={2}", currentUrl, domain.Constants.QueryString.ACTION,
                                Enums.EnMyTTAction.ForgottenPassword)
                        ,
                        VisitorType = Session.GetVisitor().VisitorType
                        ,
                        LoginIntroductoryText = myTTPage.MyTTPageLoginIntroductoryText
                        ,
                        RegisterIntroductoryText = myTTPage.MyTTPageRegisterIntroductoryText
                        ,
                        ImageUrl = myTTPage.MyTTPageMainImage.Url
                    };

If you break that into multiple lines, you should be able to figure out exactly which part is causing an issue. For example, you can create a variable like this:

var loginPageUrl = string.Format("{0}?{1}={2}", currentUrl, domain.Constants.QueryString.ACTION, Enums.EnMyTTAction.Login);

Then when constructing your MemberShipViewModel, you can assign the property to the variable value: LoginPageUrl = loginPageUrl.

Next time you get an error, you'll have a better idea of what exactly is causing it.

Alternatively, you can debug it locally by setting a breakpoint to see what's null. You can break on the error, the change the stack trace and inspect the variables. You can reduce the macro cache period so the error happens more frequently (rather than after an hour).

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Jack Gill 7 posts 77 karma points

Apr 15, 2016 @ 10:47

Thank you Nicolas so much for your help, I've managed to sort the issue. By splitting the line up like this:

    var myTTPage = new CacheController().GetCachedMyTTPage(currentNodeId);

    var model = new MembershipViewModel();

    var loginPageUrl = string.Format("{0}?{1}={2}", currentUrl, domain.Constants.QueryString.ACTION, Enums.EnMyTTAction.Login);

    var RegisterPageUrl = string.Format("{0}?{1}={2}", currentUrl, domain.Constants.QueryString.ACTION, Enums.EnMyTTAction.Register);

    var ForgottenPasswordPageUrl = string.Format("{0}?{1}={2}", currentUrl, domain.Constants.QueryString.ACTION, Enums.EnMyTTAction.ForgottenPassword);

    var VisitorType = Session.GetVisitor().VisitorType;

    var LoginIntroductoryText = myTTPage.MyTTPageLoginIntroductoryText;

    var RegisterIntroductoryText = myTTPage.MyTTPageRegisterIntroductoryText;

    var ImageUrl = myTTPage.MyTTPageMainImage.Url;

I managed to pin point the issue to the last line:

 var ImageUrl = myTTPage.MyTTPageMainImage.Url;

There wasn't an image selected in the back office causing the issue!

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Object reference not set to an instance of an object - Happens after cache reset