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AddOns screen generates 500 error



Our EpiServer CMS 7.5 site uses the LanguageManager add on and recently we're experiencing problems with this. Our users who have this plugin installed can't login anymore. When I try to go the Add-On management screen I see a popup with the following error:

[InvalidOperationException: Sequence contains more than one matching element]
System.Linq.Enumerable.SingleOrDefault(IEnumerable`1 source, Func`2 predicate) +349
EPiServer.Packaging.Storage.StateStorage.Load(String packageId, String packageVersion) +929
EPiServer.Packaging.SitePackageInfoLoader.GetPackageInfo(IPackage package, IList`1 installedPackages, IList`1 updates, IList`1 disabledPackages, Boolean tryToReload) +1171
EPiServer.Packaging.SitePackageInfoLoader.GetPackageInfo(IPackage package, Boolean tryToReload) +105
EPiServer.Packaging.SitePackageManager.GetPackageInfo(IPackage package, Boolean tryToReload) +65
System.Linq.WhereSelectListIterator`2.MoveNext() +111
NuGet.CollectionExtensions.AddRange(ICollection`1 collection, IEnumerable`1 items) +98
EPiServer.Packaging.PackageService.GetListingOperationResult(OperationResult`1 getPackagesResult) +205
EPiServer.Packaging.UI.Models.PackagesHandler.GetListOfUpdateablePackages() +88
lambda_method(Closure , ControllerBase , Object[] ) +99
System.Web.Mvc.ReflectedActionDescriptor.Execute(ControllerContext controllerContext, IDictionary`2 parameters) +209
System.Web.Mvc.ControllerActionInvoker.InvokeActionMethod(ControllerContext controllerContext, ActionDescriptor actionDescriptor, IDictionary`2 parameters) +35
System.Web.Mvc.<>c__DisplayClass15.b__12() +80
System.Web.Mvc.ControllerActionInvoker.InvokeActionMethodFilter(IActionFilter filter, ActionExecutingContext preContext, Func`1 continuation) +453
System.Web.Mvc.ControllerActionInvoker.InvokeActionMethodFilter(IActionFilter filter, ActionExecutingContext preContext, Func`1 continuation) +453
System.Web.Mvc.ControllerActionInvoker.InvokeAction(ControllerContext controllerContext, String actionName) +909
System.Web.Mvc.Controller.ExecuteCore() +129
System.Web.Mvc.ControllerBase.Execute(RequestContext requestContext) +236
EPiServer.Shell.Web.Mvc.ModuleMvcHandler.ProcessController(IController controller) +50
EPiServer.Shell.Web.Mvc.ModuleMvcHandler.BeginProcessRequest(HttpContextBase httpContext, AsyncCallback callback, Object state) +28
System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +921
System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +137

I already installed all latest versions of EPI libraries and the languagemanager via Nuget. Any thougts?

Edited, Sep 23, 2016 15:19

Check modules folder if you have some old files laying around. My guess is that you still have pieces of an old package there somewhere. Or in bin folder...

Compare vs a fresh alloy site with addons installed if you can't locate...

Sep 23, 2016 15:34

Thanks for your answer. Removing all packages and installing them again did the job on my local version of the site. However on our Azure environment the problem persists. Any other things I could try?

Sep 27, 2016 13:22

Compare bin folder and modules/modulesbin folder and try to find the difference...somewhere you got some extra dlls you don't want there. 

This is my 1000nd forum answer btw. Yey :)


Edited, Sep 27, 2016 14:36

I believe Daniel's solution is what you have to do:

  • Check bin, modules/LanguageManager (or any addon you have) and modulesbin (this is default configured in web.config <probing privatePath="modulesbin" />) folder
  • Compare those folder versus a fresh Alloy site with the same addons installed
  • You might unexpectedly deploy/copy DLL there in your development phase
  • You might install addon via web UI in old site, and now install/upgrade new nuget package by VS, it clashs.
Sep 28, 2016 6:26

How I fixed it:

1) Installed an older version of LanguageManager (latest 1.x) with NuGet.

2) Manually changed references from LanguageManager 2.x to LanguageManager 1.x in module.config/web.config/project files which NuGet somehow didn't do for me.

3) Restarted IIS.

Edited, Oct 04, 2016 9:34
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