.net 4.8: The type initializer for '<Module>' threw an exception

Question

Our software is having an issue when invoking the Windows Workflow Foundation. What's interesting is that we only have that issue when either the client or the server is updated to .Net 4.8. When both environment are running on an older version of .Net, the application works properly. Here is what I see in the logs. The interesting part is that the application work fine when self hosted. We only get this issue when going through IIS.

Event Viewer Details:

2019-11-17 22:43:31.8065 | Error |
Message :Unable to find assembly 'Test.Core, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null'.
Source : mscorlib
Stack Trace :
Server stack trace:
   at System.Runtime.Serialization.Formatters.Binary.BinaryAssemblyInfo.GetAssembly()
   at System.Runtime.Serialization.Formatters.Binary.ObjectReader.GetType(BinaryAssemblyInfo assemblyInfo, String name)
   at System.Runtime.Serialization.Formatters.Binary.ObjectMap..ctor(String objectName, String[] memberNames, BinaryTypeEnum[] binaryTypeEnumA, Object[] typeInformationA, Int32[] memberAssemIds, ObjectReader objectReader, Int32 objectId, BinaryAssemblyInfo assemblyInfo, SizedArray assemIdToAssemblyTable)
   at System.Runtime.Serialization.Formatters.Binary.__BinaryParser.ReadObjectWithMapTyped(BinaryObjectWithMapTyped record)
   at System.Runtime.Serialization.Formatters.Binary.__BinaryParser.ReadObjectWithMapTyped(BinaryHeaderEnum binaryHeaderEnum)
   at System.Runtime.Serialization.Formatters.Binary.__BinaryParser.Run()
   at System.Runtime.Serialization.Formatters.Binary.ObjectReader.Deserialize(HeaderHandler handler, __BinaryParser serParser, Boolean fCheck, Boolean isCrossAppDomain, IMethodCallMessage methodCallMessage)
   at System.Runtime.Serialization.Formatters.Binary.BinaryFormatter.Deserialize(Stream serializationStream, HeaderHandler handler, Boolean fCheck, Boolean isCrossAppDomain, IMethodCallMessage methodCallMessage)
   at System.Runtime.Remoting.Channels.CrossAppDomainSerializer.DeserializeObject(MemoryStream stm)
   at System.Runtime.Remoting.Messaging.SmuggledMethodCallMessage.FixupForNewAppDomain()
   at System.Runtime.Remoting.Channels.CrossAppDomainSink.DoDispatch(Byte[] reqStmBuff, SmuggledMethodCallMessage smuggledMcm, SmuggledMethodReturnMessage& smuggledMrm)
   at System.Runtime.Remoting.Channels.CrossAppDomainSink.DoTransitionDispatchCallback(Object[] args)

Exception rethrown at [0]:
   at System.Runtime.Remoting.Proxies.RealProxy.HandleReturnMessage(IMessage reqMsg, IMessage retMsg)
   at System.Runtime.Remoting.Proxies.RealProxy.PrivateInvoke(MessageData& msgData, Int32 type)
   at System.AppDomain.get_Id()
   at <CrtImplementationDetails>.DoCallBackInDefaultDomain(IntPtr function, Void* cookie)
   at <CrtImplementationDetails>.LanguageSupport.InitializeDefaultAppDomain(LanguageSupport* )
   at <CrtImplementationDetails>.LanguageSupport._Initialize(LanguageSupport* )
   at <CrtImplementationDetails>.LanguageSupport.Initialize(LanguageSupport* )
TargetSite : System.Reflection.Assembly GetAssembly()
***************************************
Message :The C++ module failed to load while attempting to initialize the default appdomain.

Source : Microsoft.VisualBasic.Activities.Compiler
Stack Trace :    at <CrtImplementationDetails>.LanguageSupport.Initialize(LanguageSupport* )
   at .cctor()
TargetSite : Void <CrtImplementationDetails>.LanguageSupport.Initialize(<CrtImplementationDetails>.LanguageSupport*)
***************************************
Message :The type initializer for '<Module>' threw an exception.
Source : System.Activities
Stack Trace :    at Microsoft.VisualBasic.Activities.VisualBasicHelper.Compile[T](LocationReferenceEnvironment environment, Boolean isLocationReference)
   at System.Activities.CodeActivity`1.OnInternalCacheMetadataExceptResult(Boolean createEmptyBindings)
   at Microsoft.VisualBasic.Activities.VisualBasicHelper.Compile[T](CodeActivityPublicEnvironmentAccessor publicAccessor, Boolean isLocationReference)
   at System.Activities.Activity`1.OnInternalCacheMetadata(Boolean createEmptyBindings)
   at Microsoft.VisualBasic.Activities.VisualBasicHelper.Compile[T](String expressionText, CodeActivityPublicEnvironmentAccessor publicAccessor, Boolean isLocationExpression)
   at System.Activities.Activity.InternalCacheMetadata(Boolean createEmptyBindings, IList`1& validationErrors)
   at Microsoft.VisualBasic.Activities.VisualBasicValue`1.CacheMetadata(CodeActivityMetadata metadata)
   at System.Activities.ActivityUtilities.ProcessActivity(ChildActivity childActivity, ChildActivity& nextActivity, Stack`1& activitiesRemaining, ActivityCallStack parentChain, IList`1& validationErrors, ProcessActivityTreeOptions options, ProcessActivityCallback callback)
   at System.Activities.CodeActivity`1.OnInternalCacheMetadataExceptResult(Boolean createEmptyBindings)
   at System.Activities.Activity`1.OnInternalCacheMetadata(Boolean createEmptyBindings)
   at System.Activities.ActivityUtilities.ProcessActivityTreeCore(ChildActivity currentActivity, ActivityCallStack parentChain, ProcessActivityTreeOptions options, ProcessActivityCallback callback, IList`1& validationErrors)
   at System.Activities.Activity.InternalCacheMetadata(Boolean createEmptyBindings, IList`1& validationErrors)
   at System.Activities.ActivityUtilities.CacheRootMetadata(Activity activity, LocationReferenceEnvironment hostEnvironment, ProcessActivityTreeOptions options, ProcessActivityCallback callback, IList`1& validationErrors)
   at System.Activities.Hosting.WorkflowInstance.ValidateWorkflow(WorkflowInstanceExtensionManager extensionManager)
   at System.Activities.Hosting.WorkflowInstance.RegisterExtensionManager(WorkflowInstanceExtensionManager extensionManager)
   at System.Activities.ActivityUtilities.ProcessActivity(ChildActivity childActivity, ChildActivity& nextActivity, Stack`1& activitiesRemaining, ActivityCallStack parentChain, IList`1& validationErrors, ProcessActivityTreeOptions options, ProcessActivityCallback callback)
   at System.Activities.ActivityUtilities.ProcessActivityTreeCore(ChildActivity currentActivity, ActivityCallStack parentChain, ProcessActivityTreeOptions options, ProcessActivityCallback callback, IList`1& validationErrors)
   at System.Activities.ActivityUtilities.CacheRootMetadata(Activity activity, LocationReferenceEnvironment hostEnvironment, ProcessActivityTreeOptions options, ProcessActivityCallback callback, IList`1& validationErrors)
   at System.Activities.Hosting.WorkflowInstance.ValidateWorkflow(WorkflowInstanceExtensionManager extensionManager)
   at System.Activities.Hosting.WorkflowInstance.RegisterExtensionManager(WorkflowInstanceExtensionManager extensionManager)
   at System.Activities.WorkflowApplication.EnsureInitialized()
   at System.Activities.WorkflowApplication.RunInstance(WorkflowApplication instance)
   at System.Activities.WorkflowApplication.RunInstance(WorkflowApplication instance)
   at System.Activities.WorkflowApplication.Invoke(Activity activity, IDictionary`2 inputs, WorkflowInstanceExtensionManager extensions, TimeSpan timeout)
   at System.Activities.WorkflowApplication.Invoke(Activity activity, IDictionary`2 inputs, WorkflowInstanceExtensionManager extensions, TimeSpan timeout)
   at System.Activities.WorkflowInvoker.Invoke(Activity workflow, IDictionary`2 inputs, TimeSpan timeout, WorkflowInstanceExtensionManager extensions)
   at System.Activities.WorkflowInvoker.Invoke(Activity workflow, IDictionary`2 inputs)
iis workflow-foundation

Answer 1

I cannot add a comment, but I'd like to add some more information to this issue.

Problem seems to be the BinaryFormatter: with Framework 4.8 it runs in a different AppDomain and this is a problem when your application is hosted on IIS.

I spent some time investigating with fuslogvw (logging all bindings):

With .NET 4.7 you get all the entries under the webapp folder (eg /5577f740/).

With .NET 4.8 you get an extra folder named w3wp.exe under which you find the log for the binding error (eg /5577f740/ and /w3wp.exe/).

In my case

=== Pre-bind state information ===
LOG: DisplayName = log4net, Version=2.0.8.0, Culture=neutral, PublicKeyToken=669e0ddf0bb1aa2a
 (Fully-specified)
LOG: Appbase = file:///C:/WINDOWS/SysWOW64/inetsrv/
LOG: Initial PrivatePath = NULL
LOG: Dynamic Base = NULL
LOG: Cache Base = NULL
LOG: AppName = w3wp.exe
Calling assembly : (Unknown).
===
LOG: This bind starts in default load context.
LOG: No application configuration file found.
LOG: Using host configuration file: C:\Windows\Microsoft.NET\Framework\v4.0.30319\aspnet.config
LOG: Using machine configuration file from C:\Windows\Microsoft.NET\Framework\v4.0.30319\config\machine.config.
LOG: Post-policy reference: log4net, Version=2.0.8.0, Culture=neutral, PublicKeyToken=669e0ddf0bb1aa2a
LOG: GAC Lookup was unsuccessful.
LOG: Attempting download of new URL file:///C:/WINDOWS/SysWOW64/inetsrv/log4net.DLL.
LOG: Attempting download of new URL file:///C:/WINDOWS/SysWOW64/inetsrv/log4net/log4net.DLL.
LOG: Attempting download of new URL file:///C:/WINDOWS/SysWOW64/inetsrv/log4net.EXE.
LOG: Attempting download of new URL file:///C:/WINDOWS/SysWOW64/inetsrv/log4net/log4net.EXE.
LOG: All probing URLs attempted and failed.

At the end we reverted the Framework version to 4.7 in our boxes.

Answer 2

I had exactly the same issue with .NET 4.8. When running the workflow in a console application, there were no errors. When running the workflow in IIS, the same ModuleLoadException was thrown. The same code ran perfectly in .NET 4.7 or earlier. It seems that not all workflows (ie .XAML files) would trigger this bug. I didn't use WorkflowInvoker.Invoke to run workflows, but use ActivityXamlServices.Load() instead.

Looks like a Microsoft bug to me.

Answer 3

Followup on this. We noticed that this issue was only happening in C# workflows that had VB expressions. Replacing every VB expression by a C# expression fixed the issue.