RazorLight Could not load file or assembly System.Threading.AccessControl

The goal is to generate HTML from a .cshtml file

When using RazorLight I get the following error:

    System.IO.FileNotFoundException: Could not load file or assembly 'System.Threading.AccessControl, Version=4.0.5.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a'. The system cannot find the file specified.
File name: 'System.Threading.AccessControl, Version=4.0.5.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a'
   at System.Reflection.RuntimeAssembly.nLoad(AssemblyName fileName, String codeBase, RuntimeAssembly assemblyContext, StackCrawlMark& stackMark, Boolean throwOnFileNotFound, AssemblyLoadContext assemblyLoadContext)
   at System.Reflection.RuntimeAssembly.InternalLoadAssemblyName(AssemblyName assemblyRef, StackCrawlMark& stackMark, AssemblyLoadContext assemblyLoadContext)
   at System.Reflection.Assembly.Load(AssemblyName assemblyRef, StackCrawlMark& stackMark, AssemblyLoadContext assemblyLoadContext)
   at System.Reflection.Assembly.Load(AssemblyName assemblyRef)
   at RazorLight.Compilation.DefaultMetadataReferenceManager.GetReferencedAssemblies(Assembly a, IEnumerable`1 excludedAssemblies, HashSet`1 visitedAssemblies)+MoveNext()
   at RazorLight.Compilation.DefaultMetadataReferenceManager.GetReferencedAssemblies(Assembly a, IEnumerable`1 excludedAssemblies, HashSet`1 visitedAssemblies)+MoveNext()
   at RazorLight.Compilation.DefaultMetadataReferenceManager.GetReferencedAssemblies(Assembly a, IEnumerable`1 excludedAssemblies, HashSet`1 visitedAssemblies)+MoveNext()
   at System.Linq.Set`1.UnionWith(IEnumerable`1 other)
   at System.Linq.Enumerable.UnionIterator`1.FillSet()
   at System.Linq.Enumerable.UnionIterator`1.ToArray()
   at System.Linq.Enumerable.ToArray[TSource](IEnumerable`1 source)
   at RazorLight.Compilation.DefaultMetadataReferenceManager.Resolve(Assembly assembly, DependencyContext dependencyContext)
   at RazorLight.Compilation.DefaultMetadataReferenceManager.Resolve(Assembly assembly)
   at RazorLight.Compilation.RoslynCompilationService.EnsureOptions()
   at RazorLight.Compilation.RoslynCompilationService.get_ParseOptions()
   at RazorLight.Compilation.RoslynCompilationService.CreateSyntaxTree(SourceText sourceText)
   at RazorLight.Compilation.RoslynCompilationService.CreateCompilation(String compilationContent, String assemblyName)
   at RazorLight.Compilation.RoslynCompilationService.CompileAndEmit(IGeneratedRazorTemplate razorTemplate)
   at RazorLight.Compilation.RazorTemplateCompiler.CompileAndEmit(RazorLightProjectItem projectItem)
   at RazorLight.Compilation.RazorTemplateCompiler.OnCacheMissAsync(String templateKey)

I installed the NuGet package RazorLight 2.0.0-rc.3 and this is my code to generate html from a .cshtml file:

private async Task<string> RenderRazorTemplate(string key, Type viewModelType, object viewModel)
{
  var engine = new RazorLightEngineBuilder()
    .UseEmbeddedResourcesProject(Assembly.GetExecutingAssembly()) // Use the Executing Assembly as project that embeds the .cshtml templates
    .SetOperatingAssembly(viewModelType.Assembly) // Without this, you'll get a Exception saying that the Assembly can't find the AntiForgery.dll
    .UseMemoryCachingProvider()
    .Build();
            
  return await engine.CompileRenderAsync(key, viewModel);
}

Trying to add the System.Threading.AccessControl NuGet Package, but then another file or assembly can't be loaded (so never ending story of adding packages). There must be another solution.

I am using .NET Core 3.1.

For me the issue was that the Engine was used in a IRequestHandler from Mediatr.

Outsourcing the engine to the controller instead of having it inside the IRequestHandler fixed the issue.