Getting null reference exception when try to open list settings (Listedit.aspx) for Sharepoint 2010

This is a typical  error scenario that you have if you move or copy some sharepoint core dll’s which is referenced fr0m another folder.There is common mistake when developing custom applications that moving and copying sharepoint core dll’s to where is not in original folder (for example coping Microsoft.Sharepoint.dll to BIN folder of web application)  or unnecesserly register in GAC (for example registering Microsoft.Sharepoint.ApplicationPages.dll to GAC).

Why is this dangerous ? i can simply say when you upgrade or install any patch on sharepoint , the copied dlls form original location  can not be upgraded  by default .So this cause a huge anomality in your system. DLL version integrity is very important issue for every Microsoft product. So be careful for this operations , after all if you still need to copy or move operation, that upgrading copied dlls is your responsibility.

So lets keep going with our error :

when you click the one of list’s list settings (listedit.aspx) you can probably getting fallowing error in application event logs:

Exception information:
Exception type: NullReferenceException
Exception message: Object reference not set to an instance of an object.

Stack trace:    at Microsoft.SharePoint.ApplicationPages.ListEditPage.SetSectionLinks()
at Microsoft.SharePoint.ApplicationPages.ListEditPage.OnLoad(EventArgs e)
at ASP._layouts_listedit_aspx.OnLoad(EventArgs e) in c:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\14\TEMPLATE\LAYOUTS\listedit.aspx:line 25
at System.Web.UI.Control.LoadRecursive()
at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)

And if you enable custom errors from  in your web.config which is in Layouts folder.You can see the error in browser:

NullReferenceException: Object reference not set to an instance of an object.]
Microsoft.SharePoint.ApplicationPages.ListEditPage.SetSectionLinks() +426
Microsoft.SharePoint.ApplicationPages.ListEditPage.OnLoad(EventArgs e) +896
ASP._layouts_listedit_aspx.OnLoad(EventArgs e) +290
System.Web.UI.Control.LoadRecursive() +65
System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +2427

For resolving this issue you should find the related copied assembly files which according this scenario is Microsoft.Sharepoint.ApplicationPages.dll in use for unfamiliar locations.

the orginal location for this dll is  Drive:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\14\CONFIG\BIN

1) First Check the GAC this dll should not be added to GAC if it is upgrade latest correct version or delete the dll.
2) Check other possible existance may it be used in BIN folders of web applications. For getting all list of any dll location you can use this script:
http://blog.bugrapostaci.com/2011/12/26/powershell-find-files-with-versions/ this powershell command gives you a list that defined dll locations and versions.

For best practise if you need any reference to Sharepoint DLL’s use and reference them in original locations .if not you always remember to upgrade latest versions where it have been that is your resposibility.

See you next time.