IIS manager GUI not working (Method not found)

Issue: IIS manager GUI not working.  

When user is opening up IIS manager and trying to browse the application pools then we are getting below error message. 

"Method not found:  Microsoft.Web.Administration.StartModeMicrosoft.Web.Administration.ApplicationPool.get_StartMode()". 

Cause: Server is loading older version of "Microsoft.Web.Administration.dll" from C:\Windows\assembly\GAC_MSIL\Microsoft.Web.Administration\7.0.0.0__31bf3856ad364e35 GAC folder.

Resolution:

1. Please take the backup of C:\Windows\assembly\GAC_MSIL\Microsoft.Web.Administration\7.0.0.0__31bf3856ad364e35 folder. 
2. After that copy "C:\Windows\System32\inetsrv\Microsoft.Web.Administration.dll" dll and paste it into C:\Windows\assembly\GAC_MSIL\Microsoft.Web.Administration\7.0.0.0__31bf3856ad364e35 folder. 
3. After that you should be able to browse the Application Pool in IIS Manager.