Loading this assembly would produce a different grant set from other instances. (Exception from HRESULT: 0x80131401)
We have SharePoint 2013 Servers that were patched with windows updates and since then we are receiving the following error. We have restarted the servers, removed the windows updates manually and then restarted the servers, restored to a copy of windows server before the windows update but the error is persisting. We have also removed the temporary files from Windows directory and nothing is helping.
I have attached a screenshot of the Windows Updates that were applied to our servers overnight
Loading this assembly would produce a different grant set from other instances. (Exception from HRESULT: 0x80131401)
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.
Exception Details: System.IO.FileLoadException: Loading this assembly would produce a different grant set from other instances. (Exception from HRESULT: 0x80131401)
Source Error:
An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.
Stack Trace:
[FileLoadException: Loading this assembly would produce a different grant set from other instances. (Exception from HRESULT: 0x80131401)]
System.Linq.Enumerable.Any(IEnumerable`1 source) +0
System.Web.Compilation.BuildManager.GetPreStartInitMethodsFromAssemblyCollection(IEnumerable`1 assemblies, Boolean buildingFromCache) +210
System.Web.Compilation.BuildManager.CallPreStartInitMethods(String preStartInitListPath, Boolean& isRefAssemblyLoaded) +98
System.Web.Compilation.BuildManager.ExecutePreAppStart() +139
System.Web.Hosting.HostingEnvironment.Initialize(ApplicationManager appManager, IApplicationHost appHost, IConfigMapPathFactory configMapPathFactory, HostingEnvironmentParameters hostingParameters, PolicyLevel policyLevel, Exception appDomainCreationException) +1005
[HttpException (0x80004005): Loading this assembly would produce a different grant set from other instances. (Exception from HRESULT: 0x80131401)]
System.Web.HttpRuntime.FirstRequestInit(HttpContext context) +646
System.Web.HttpRuntime.EnsureFirstRequestInit(HttpContext context) +159
System.Web.HttpRuntime.ProcessRequestNotificationPrivate(IIS7WorkerRequest wr, HttpContext context) +779
--------------------------------------------------------------------------------
Version Information: Microsoft .NET Framework Version:4.0.30319; ASP.NET Version:4.0.30319.36366
Answer
I ran into the same exception when developing on Sitecore, and an iisreset cleared the issue.