ASP.NET MVC 4 Website won't start - Could not load type 'System.Reflection.AssemblyMetadataAttribute' - asp.net-mvc-4

Question

I deployed my ASP.NET MVC 4 web app to a Windows Server 2003 (IIS 6). But it will not start.
Originally I had developed the project for .NET 4.5, but had to rebuild it for .NET4 when I found out that .NET 4.5 is not supported on Windows Server 2003.
This meant removing all the third party references (with NuGet), changing the build target in project properties to .NET4, then adding the references back.
The references were to Ninject, EF and Automapper.
When I try to load a page I get the following error:
Could not load type 'System.Reflection.AssemblyMetadataAttribute' from
assembly 'mscorlib, Version=4.0.0.0, Culture=neutral,
PublicKeyToken=b77a5c561934e089'. 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.TypeLoadException: Could not load type
'System.Reflection.AssemblyMetadataAttribute' from assembly 'mscorlib,
Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089'.
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:
[TypeLoadException: Could not load type
'System.Reflection.AssemblyMetadataAttribute' from assembly 'mscorlib,
Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089'.]
System.ModuleHandle.ResolveType(RuntimeModule module, Int32 typeToken,
IntPtr* typeInstArgs, Int32 typeInstCount, IntPtr* methodInstArgs,
Int32 methodInstCount, ObjectHandleOnStack type) +0
System.ModuleHandle.ResolveTypeHandleInternal(RuntimeModule module,
Int32 typeToken, RuntimeTypeHandle[] typeInstantiationContext,
RuntimeTypeHandle[] methodInstantiationContext) +180
System.Reflection.RuntimeModule.ResolveType(Int32 metadataToken,
Type[] genericTypeArguments, Type[] genericMethodArguments) +192
System.Reflection.CustomAttribute.FilterCustomAttributeRecord(CustomAttributeRecord
caRecord, MetadataImport scope, Assembly& lastAptcaOkAssembly,
RuntimeModule decoratedModule, MetadataToken decoratedToken,
RuntimeType attributeFilterType, Boolean mustBeInheritable, Object[]
attributes, IList derivedAttributes, RuntimeType& attributeType,
IRuntimeMethodInfo& ctor, Boolean& ctorHasParameters, Boolean&
isVarArg) +115
System.Reflection.CustomAttribute.GetCustomAttributes(RuntimeModule
decoratedModule, Int32 decoratedMetadataToken, Int32 pcaCount,
RuntimeType attributeFilterType, Boolean mustBeInheritable, IList
derivedAttributes, Boolean isDecoratedTargetSecurityTransparent) +426
System.Reflection.CustomAttribute.GetCustomAttributes(RuntimeAssembly
assembly, RuntimeType caType) +103
System.Reflection.RuntimeAssembly.GetCustomAttributes(Type
attributeType, Boolean inherit) +64
WebActivator.AssemblyExtensions.GetActivationAttributes(Assembly
assembly) +113
WebActivator.ActivationManager.RunActivationMethods() +216
WebActivator.ActivationManager.RunPreStartMethods() +28
WebActivator.ActivationManager.Run() +55
[InvalidOperationException: The pre-application start initialization
method Run on type WebActivator.ActivationManager threw an exception
with the following error message: Could not load type
'System.Reflection.AssemblyMetadataAttribute' from assembly 'mscorlib,
Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089'..]
System.Web.Compilation.BuildManager.InvokePreStartInitMethods(ICollection`1
methods) +423
System.Web.Compilation.BuildManager.CallPreStartInitMethods() +306
System.Web.Hosting.HostingEnvironment.Initialize(ApplicationManager
appManager, IApplicationHost appHost, IConfigMapPathFactory
configMapPathFactory, HostingEnvironmentParameters hostingParameters,
PolicyLevel policyLevel, Exception appDomainCreationException) +677
[HttpException (0x80004005): The pre-application start initialization
method Run on type WebActivator.ActivationManager threw an exception
with the following error message: Could not load type
'System.Reflection.AssemblyMetadataAttribute' from assembly 'mscorlib,
Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089'..]
System.Web.HttpRuntime.FirstRequestInit(HttpContext context) +9164848
System.Web.HttpRuntime.EnsureFirstRequestInit(HttpContext context) +97
System.Web.HttpRuntime.ProcessRequestInternal(HttpWorkerRequest wr)
+258
Any ideas?
EDIT: Website developed using VS2012

Answer 1

Could not load type 'System.Runtime.CompilerServices.ExtensionAttribute' from assembly mscorlib
Yes, this technically can go wrong when you execute code on .NET 4.0 instead of .NET 4.5. The attribute was moved from System.Core.dll to mscorlib.dll in .NET 4.5. While that sounds like a rather nasty breaking change in a framework version that is supposed to be 100% compatible, a [TypeForwardedTo] attribute is supposed to make this difference unobservable.