Cannot load a reference assembly for execution

All of a sudden my website is not loading and giving me below error. I am running VS2017 with .Net Framework 4.7.1 on Windows 10 Home.

[BadImageFormatException: Cannot load a reference assembly for execution.]

[BadImageFormatException: Could not load file or assembly 'System.IO.Compression.ZipFile' 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.InternalLoadAssemblyName(AssemblyName assemblyRef, Evidence assemblySecurity, RuntimeAssembly reqAssembly, StackCrawlMark& stackMark, IntPtr pPrivHostBinder, Boolean throwOnFileNotFound, Boolean forIntrospection, Boolean suppressSecurityChecks) +225
   System.Reflection.RuntimeAssembly.InternalLoad(String assemblyString, Evidence assemblySecurity, StackCrawlMark& stackMark, IntPtr pPrivHostBinder, Boolean forIntrospection) +110
   System.Reflection.RuntimeAssembly.InternalLoad(String assemblyString, Evidence assemblySecurity, StackCrawlMark& stackMark, Boolean forIntrospection) +22
   System.Reflection.Assembly.Load(String assemblyString) +34
   System.Web.Configuration.CompilationSection.LoadAssemblyHelper(String assemblyName, Boolean starDirective) +48

[ConfigurationErrorsException: Could not load file or assembly 'System.IO.Compression.ZipFile' 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) +729
   System.Web.Configuration.CompilationSection.LoadAllAssembliesFromAppDomainBinDirectory() +247
   System.Web.Configuration.CompilationSection.LoadAssembly(AssemblyInfo ai) +157
   System.Web.Compilation.BuildManager.GetReferencedAssemblies(CompilationSection compConfig) +226
   System.Web.Compilation.BuildManager.GetPreStartInitMethodsFromReferencedAssemblies() +73
   System.Web.Compilation.BuildManager.CallPreStartInitMethods(String preStartInitListPath, Boolean& isRefAssemblyLoaded) +321
   System.Web.Compilation.BuildManager.ExecutePreAppStart() +170
   System.Web.Hosting.HostingEnvironment.Initialize(ApplicationManager appManager, IApplicationHost appHost, IConfigMapPathFactory configMapPathFactory, HostingEnvironmentParameters hostingParameters, PolicyLevel policyLevel, Exception appDomainCreationException) +734

[HttpException (0x80004005): Could not load file or assembly 'System.IO.Compression.ZipFile' 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) +525
   System.Web.HttpRuntime.EnsureFirstRequestInit(HttpContext context) +118
   System.Web.HttpRuntime.ProcessRequestNotificationPrivate(IIS7WorkerRequest wr, HttpContext context) +708

Any suggestions?

What worked for me was deleting the bin and obj directories under my web app then rebuilding.

There's a known issue with .NET Framework 4.7.1 in this regard. Supposedly sorted in 4.7.2, but in the meantime what can you do?

The issue is related to the serialization assemblies, which you can optionally set to generate or not as part of your build (rclick project -> Properties -> Build tab -> see 'Generate serialization assemblies' at bottom.)

What worked for me - and I'm standing on the shoulders of others in part here - is to ensure this setting is set to 'Auto'. Do a full 'clean solution', and additionally if paranoid, this PowerShell snippet is handy if run in your solution root folder:

Get-ChildItem .\ -include bin,obj -Recurse | foreach ($_) { remove-item $_.fullname -Force -Recurse }

Next, add the following targets to your csproj (just inside the enclosing <Project> tag:

<Target Name="RemoveDesignTimeFacadesBeforeSGen" BeforeTargets="GenerateSerializationAssemblies">
    <ItemGroup>
      <ReferencePath Remove="@(_DesignTimeFacadeAssemblies_Names->'%(OriginalIdentity)')" />
    </ItemGroup>
    <Message Importance="normal" Text="Removing DesignTimeFacades from ReferencePath before running SGen." />
  </Target>
  <Target Name="ReAddDesignTimeFacadesBeforeSGen" AfterTargets="GenerateSerializationAssemblies">
    <ItemGroup>
      <ReferencePath Include="@(_DesignTimeFacadeAssemblies_Names->'%(OriginalIdentity)')" />
    </ItemGroup>
    <Message Importance="normal" Text="Adding back DesignTimeFacades from ReferencePath now that SGen has run." />
  </Target>

If still no luck, explicitly set 'Generate serialization assemblies' to 'On' to force generation, and rebuild & run.

Today I have installed Acumatica 2018 R1 and I have come across this issue. Removing System.IO.Compression.ZipFile from bin folder fixed the problem.