.Net 4.6 website not loading Reference Assemblies correctly

Question

I have a web project in Visual Studio 2013, including several library projects.

Problem is that adding a reference (ie. System.Collection, System.Net) to the web project is being added as a 'Reference Assembly' from C:\Program Files (x86)\Reference Assemblies\Microsoft, when loaded in IIS it is not correctly loading the implementation of the assembly (from GAC). Example error follows.

[BadImageFormatException: Cannot load a reference assembly for execution.]  [BadImageFormatException: Could not load file or assembly 'System.Collections' or one of its dependencies. Reference assemblies should not be loaded for execution.  They can only be loaded in the Reflection-only loader context. (Exception from HRESULT: 0x80131058)]    System.Reflection.RuntimeAssembly._nLoad(AssemblyName fileName, String codeBase, Evidence assemblySecurity, RuntimeAssembly locationHint, StackCrawlMark& stackMark, IntPtr pPrivHostBinder, Boolean throwOnFileNotFound, Boolean forIntrospection, Boolean suppressSecurityChecks) +0    System.Reflection.RuntimeAssembly.nLoad(AssemblyName fileName, String codeBase, Evidence assemblySecurity, RuntimeAssembly locationHint, StackCrawlMark& stackMark, IntPtr pPrivHostBinder, Boolean throwOnFileNotFound, Boolean forIntrospection, Boolean suppressSecurityChecks) +34    System.Reflection.RuntimeAssembly.InternalLoadAssemblyName(AssemblyName assemblyRef, Evidence assemblySecurity, RuntimeAssembly reqAssembly, StackCrawlMark& stackMark, IntPtr pPrivHostBinder, Boolean throwOnFileNotFound, Boolean forIntrospection, Boolean suppressSecurityChecks) +152    System.Reflection.RuntimeAssembly.InternalLoad(String assemblyString, Evidence assemblySecurity, StackCrawlMark& stackMark, IntPtr pPrivHostBinder, Boolean forIntrospection) +77    System.Reflection.RuntimeAssembly.InternalLoad(String assemblyString, Evidence assemblySecurity, StackCrawlMark& stackMark, Boolean forIntrospection) +16    System.Reflection.Assembly.Load(String assemblyString) +28    System.Web.Configuration.CompilationSection.LoadAssemblyHelper(String assemblyName, Boolean starDirective) +38  [ConfigurationErrorsException: Could not load file or assembly 'System.Collections' or one of its dependencies. Reference assemblies should not be loaded for execution.  They can only be loaded in the Reflection-only loader context. (Exception from HRESULT: 0x80131058)]    System.Web.Configuration.CompilationSection.LoadAssemblyHelper(String assemblyName, Boolean starDirective) +728    System.Web.Configuration.CompilationSection.LoadAllAssembliesFromAppDomainBinDirectory() +196    System.Web.Configuration.CompilationSection.LoadAssembly(AssemblyInfo ai) +45    System.Web.Compilation.BuildManager.GetReferencedAssemblies(CompilationSection compConfig) +172    System.Web.Compilation.BuildManager.GetPreStartInitMethodsFromReferencedAssemblies() +91    System.Web.Compilation.BuildManager.CallPreStartInitMethods(String preStartInitListPath, Boolean& isRefAssemblyLoaded) +111    System.Web.Compilation.BuildManager.ExecutePreAppStart() +156    System.Web.Hosting.HostingEnvironment.Initialize(ApplicationManager appManager, IApplicationHost appHost, IConfigMapPathFactory configMapPathFactory, HostingEnvironmentParameters hostingParameters, PolicyLevel policyLevel, Exception appDomainCreationException) +624  [HttpException (0x80004005): Could not load file or assembly 'System.Collections' or one of its dependencies. Reference assemblies should not be loaded for execution.  They can only be loaded in the Reflection-only loader context. (Exception from HRESULT: 0x80131058)]    System.Web.HttpRuntime.FirstRequestInit(HttpContext context) +659    System.Web.HttpRuntime.EnsureFirstRequestInit(HttpContext context) +95    System.Web.HttpRuntime.ProcessRequestNotificationPrivate(IIS7WorkerRequest wr, HttpContext context) +189 

Deleting the reference dlls from the bin folder fixes the issue, but I am not sure what needs changing to fix this properly.

Answer 1

I delete the package from the /Bin folder

System.Collections and System.Collections.Concurrent

and rebuild project

its works.