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PropertyFor exceptions: Value cannot be null. Parameter name: key + An item with the same key has already been added

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I'm investigating the following two exceptions on a 9.12.3 MVC site running on Azure.

The line number references @Html.PropertyFor()-calls from the view for different ContentArea properties.

The exceptions seem to occurs randomly for different requests it seems. Also seems that certain pages have a lot more errors of this kind than others. For example I haven't seen the error on the start page in any error logging.

Anyone else seen and solved something like this?

I'm thinking thread safety or caching issue but am open for just about anything.

Exception: An item with the same key has already been added.
Stack trace
at System.Web.HttpServerUtility.ExecuteInternal(IHttpHandler handler, TextWriter writer, Boolean preserveForm, Boolean setPreviousPage, VirtualPath path, VirtualPath filePath, String physPath, Exception error, String queryStringOverride)
at System.Web.HttpServerUtility.Execute(IHttpHandler handler, TextWriter writer, Boolean preserveForm, Boolean setPreviousPage)
at System.Web.HttpServerUtility.Execute(IHttpHandler handler, TextWriter writer, Boolean preserveForm)
at System.Web.Mvc.ViewPage.RenderView(ViewContext viewContext)
at System.Web.Mvc.ViewUserControl.RenderViewAndRestoreContentType(ViewPage containerPage, ViewContext viewContext)
at System.Web.Mvc.ViewUserControl.RenderView(ViewContext viewContext)
at System.Web.Mvc.Html.TemplateHelpers.ActionCacheViewItem.Execute(HtmlHelper html, ViewDataDictionary viewData)
at System.Web.Mvc.Html.TemplateHelpers.ExecuteTemplate(HtmlHelper html, ViewDataDictionary viewData, String templateName, DataBoundControlMode mode, GetViewNamesDelegate getViewNames, GetDefaultActionsDelegate getDefaultActions)
at System.Web.Mvc.Html.TemplateHelpers.TemplateHelper(HtmlHelper html, ModelMetadata metadata, String htmlFieldName, String templateName, DataBoundControlMode mode, Object additionalViewData, ExecuteTemplateDelegate executeTemplate)
at System.Web.Mvc.Html.TemplateHelpers.TemplateHelper(HtmlHelper html, ModelMetadata metadata, String htmlFieldName, String templateName, DataBoundControlMode mode, Object additionalViewData)
at System.Web.Mvc.Html.TemplateHelpers.TemplateFor[TContainer,TValue](HtmlHelper`1 html, Expression`1 expression, String templateName, String htmlFieldName, DataBoundControlMode mode, Object additionalViewData)
at System.Web.Mvc.Html.DisplayExtensions.DisplayFor[TModel,TValue](HtmlHelper`1 html, Expression`1 expression, Object additionalViewData)
at Customer.Core.PropertyRenderers.SitePropertyRenderer.PropertyFor[TModel,TValue](HtmlHelper`1 html, String viewModelPropertyName, Object additionalViewData, Object editorSettings, Expression`1 expression, Func`2 displayForAction)
at EPiServer.Web.Mvc.Html.PropertyExtensions.PropertyFor[TModel,TValue](HtmlHelper`1 html, Expression`1 expression, Object additionalViewData)
at ASP._Page_Views_Shared_Molecules_Footer_cshtml.Execute() in d:\home\site\wwwroot\Views\Shared\Molecules\Footer.cshtml:line 16
at System.Web.WebPages.WebPageBase.ExecutePageHierarchy()
at System.Web.Mvc.WebViewPage.ExecutePageHierarchy()
at System.Web.WebPages.WebPageBase.ExecutePageHierarchy(WebPageContext pageContext, TextWriter writer, WebPageRenderingBase startPage)
at System.Web.Mvc.Html.PartialExtensions.Partial(HtmlHelper htmlHelper, String partialViewName, Object model, ViewDataDictionary viewData)
at ASP._Page_Views_Shared_Layouts_Standard_cshtml.Execute() in d:\home\site\wwwroot\Views\Shared\Layouts\Standard.cshtml:line 49
at System.Web.WebPages.WebPageBase.ExecutePageHierarchy()
at System.Web.Mvc.WebViewPage.ExecutePageHierarchy()
at System.Web.WebPages.WebPageBase.ExecutePageHierarchy(WebPageContext pageContext, TextWriter writer, WebPageRenderingBase startPage)
at System.Web.WebPages.WebPageBase.<>c__DisplayClass3.b__2(TextWriter writer)
at System.Web.WebPages.WebPageExecutingBase.WriteTo(TextWriter writer, HelperResult content)
at System.Web.WebPages.WebPageBase.RenderSurrounding(String partialViewName, Action`1 body)
at System.Web.WebPages.WebPageBase.PopContext()
at System.Web.Mvc.ViewResultBase.ExecuteResult(ControllerContext context)
at System.Web.Mvc.ControllerActionInvoker.InvokeActionResultFilterRecursive(IList`1 filters, Int32 filterIndex, ResultExecutingContext preContext, ControllerContext controllerContext, ActionResult actionResult)
at System.Web.Mvc.ControllerActionInvoker.InvokeActionResultFilterRecursive(IList`1 filters, Int32 filterIndex, ResultExecutingContext preContext, ControllerContext controllerContext, ActionResult actionResult)
at System.Web.Mvc.ControllerActionInvoker.InvokeActionResultFilterRecursive(IList`1 filters, Int32 filterIndex, ResultExecutingContext preContext, ControllerContext controllerContext, ActionResult actionResult)
at System.Web.Mvc.ControllerActionInvoker.InvokeActionResultFilterRecursive(IList`1 filters, Int32 filterIndex, ResultExecutingContext preContext, ControllerContext controllerContext, ActionResult actionResult)
at System.Web.Mvc.ControllerActionInvoker.InvokeActionResultFilterRecursive(IList`1 filters, Int32 filterIndex, ResultExecutingContext preContext, ControllerContext controllerContext, ActionResult actionResult)
at System.Web.Mvc.ControllerActionInvoker.InvokeActionResultFilterRecursive(IList`1 filters, Int32 filterIndex, ResultExecutingContext preContext, ControllerContext controllerContext, ActionResult actionResult)
at System.Web.Mvc.ControllerActionInvoker.InvokeActionResultFilterRecursive(IList`1 filters, Int32 filterIndex, ResultExecutingContext preContext, ControllerContext controllerContext, ActionResult actionResult)
at System.Web.Mvc.ControllerActionInvoker.InvokeActionResultWithFilters(ControllerContext controllerContext, IList`1 filters, ActionResult actionResult)
at System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass21.b__1e(IAsyncResult asyncResult)

And this one...

Exception: Value cannot be null. Parameter name: key

Stack trace
at System.Web.HttpServerUtility.ExecuteInternal(IHttpHandler handler, TextWriter writer, Boolean preserveForm, Boolean setPreviousPage, VirtualPath path, VirtualPath filePath, String physPath, Exception error, String queryStringOverride)
at System.Web.HttpServerUtility.Execute(IHttpHandler handler, TextWriter writer, Boolean preserveForm, Boolean setPreviousPage)
at System.Web.HttpServerUtility.Execute(IHttpHandler handler, TextWriter writer, Boolean preserveForm)
at System.Web.Mvc.ViewPage.RenderView(ViewContext viewContext)
at System.Web.Mvc.ViewUserControl.RenderViewAndRestoreContentType(ViewPage containerPage, ViewContext viewContext)
at System.Web.Mvc.ViewUserControl.RenderView(ViewContext viewContext)
at System.Web.Mvc.Html.TemplateHelpers.ExecuteTemplate(HtmlHelper html, ViewDataDictionary viewData, String templateName, DataBoundControlMode mode, GetViewNamesDelegate getViewNames, GetDefaultActionsDelegate getDefaultActions)
at System.Web.Mvc.Html.TemplateHelpers.TemplateHelper(HtmlHelper html, ModelMetadata metadata, String htmlFieldName, String templateName, DataBoundControlMode mode, Object additionalViewData, ExecuteTemplateDelegate executeTemplate)
at System.Web.Mvc.Html.TemplateHelpers.TemplateHelper(HtmlHelper html, ModelMetadata metadata, String htmlFieldName, String templateName, DataBoundControlMode mode, Object additionalViewData)
at System.Web.Mvc.Html.TemplateHelpers.TemplateFor[TContainer,TValue](HtmlHelper`1 html, Expression`1 expression, String templateName, String htmlFieldName, DataBoundControlMode mode, Object additionalViewData)
at System.Web.Mvc.Html.DisplayExtensions.DisplayFor[TModel,TValue](HtmlHelper`1 html, Expression`1 expression, Object additionalViewData)
at Customer.Core.PropertyRenderers.SitePropertyRenderer.PropertyFor[TModel,TValue](HtmlHelper`1 html, String viewModelPropertyName, Object additionalViewData, Object editorSettings, Expression`1 expression, Func`2 displayForAction)
at EPiServer.Web.Mvc.Html.PropertyExtensions.PropertyFor[TModel,TValue](HtmlHelper`1 html, Expression`1 expression, Object additionalViewData)
at ASP._Page_Views_SubSiteStartPage_Index_cshtml.Execute() in d:\home\site\wwwroot\Views\SubSiteStartPage\Index.cshtml:line 18
at System.Web.WebPages.WebPageBase.ExecutePageHierarchy()
at System.Web.Mvc.WebViewPage.ExecutePageHierarchy()
at System.Web.WebPages.StartPage.ExecutePageHierarchy()
at System.Web.WebPages.WebPageBase.ExecutePageHierarchy(WebPageContext pageContext, TextWriter writer, WebPageRenderingBase startPage)
at System.Web.Mvc.ViewResultBase.ExecuteResult(ControllerContext context)
at System.Web.Mvc.ControllerActionInvoker.InvokeActionResultFilterRecursive(IList`1 filters, Int32 filterIndex, ResultExecutingContext preContext, ControllerContext controllerContext, ActionResult actionResult)
at System.Web.Mvc.ControllerActionInvoker.InvokeActionResultFilterRecursive(IList`1 filters, Int32 filterIndex, ResultExecutingContext preContext, ControllerContext controllerContext, ActionResult actionResult)
at System.Web.Mvc.ControllerActionInvoker.InvokeActionResultFilterRecursive(IList`1 filters, Int32 filterIndex, ResultExecutingContext preContext, ControllerContext controllerContext, ActionResult actionResult)
at System.Web.Mvc.ControllerActionInvoker.InvokeActionResultFilterRecursive(IList`1 filters, Int32 filterIndex, ResultExecutingContext preContext, ControllerContext controllerContext, ActionResult actionResult)
at System.Web.Mvc.ControllerActionInvoker.InvokeActionResultFilterRecursive(IList`1 filters, Int32 filterIndex, ResultExecutingContext preContext, ControllerContext controllerContext, ActionResult actionResult)
at System.Web.Mvc.ControllerActionInvoker.InvokeActionResultFilterRecursive(IList`1 filters, Int32 filterIndex, ResultExecutingContext preContext, ControllerContext controllerContext, ActionResult actionResult)
at System.Web.Mvc.ControllerActionInvoker.InvokeActionResultFilterRecursive(IList`1 filters, Int32 filterIndex, ResultExecutingContext preContext, ControllerContext controllerContext, ActionResult actionResult)
at System.Web.Mvc.ControllerActionInvoker.InvokeActionResultWithFilters(ControllerContext controllerContext, IList`1 filters, ActionResult actionResult)
at System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass21.b__1e(IAsyncResult asyncResult)

#170754
Oct 28, 2016 12:33
Vote:
 

I haven't seen the app log these errors again after updating StructureMap... 9 days and counting.

http://krompaco.nu/2016/11/upgrade-structuremap-to-3-1-9-463/

#172218
Nov 27, 2016 23:23
Vote:
 

UPDATE: StructureMap update made it less frequent but later on we still saw the error pop up here and there.

Thing the main cause was that we were modifying ContentAreaItem.RenderSettings runtime.

Dev support also logged a bug related to this issue so that it will be easy to spot in the future: 
#CMS-6181 ContentAreaItem does not throw when changing read-only values

#175756
Edited, Mar 01, 2017 11:13
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