“Cannot find compilation library location for package ”enc.dll“” error occur .net core dependency injection

问题

I am building a website using asp.net core mvc, and for the login i added dependency for enc.dll file, which just encrypt/decrypt user information. I made a Seeder class with enc.dll file, which has a key property and en/decrypt with the key. Then I added it to my service to use dependency injection feature.

services.AddSingleton<ISeeder, Seeder>();

While it works well when i call enc, dec function of seeder class, it does not return any error. Below is the example code.

    private readonly ISeeder seed;
    public AccountController(ISeeder seed)
    {
        this.seed = seed;
    }

    [HttpGet]
    public IActionResult test()
    {
        string s = seed.Enc("testEncode");
        return Json(s);
    }

So it works when i return string s that is created by seed instance.

but it is not working when i try to return a view without using seed instance and throwing an error, where Enc is the dll library i am using.

InvalidOperationException: Cannot find compilation library location for package 'Enc'
Microsoft.Extensions.DependencyModel.CompilationLibrary.ResolveReferencePaths(ICompilationAssemblyResolver resolver, List<string> assemblies)

And below is my Seeder code.

 private Enc enc;
    private readonly EncKey key;
    public Seeder(IOptions<EncKey> options)
    {
        enc = new Enc();
        key = options.Value;
    }

    public string Dec(string toDec)
    {
        return enc.Dec(toDec, key.EncryptKey);
    }

    public string Enc(string toEnc)
    {
        return enc.Enc(toEnc, key.EncryptKey);
    }

Could anyone help? I am working on .net core 2.0 environment

回答1:

UPDATE

This issue was fixed in 2.0.3, for apply need to update VS(or manualy dotnet SDK and Runtime) and project packages via nuget(in particular Microsoft.AspNetCore.All to 2.0.3)

It's known issue of .Net Core 2.0 https://github.com/dotnet/core-setup/issues/2981

Razor view precompilation can not resolve lib path

Here workaround to get this work:

add this (it's fixing release publish error)

using Microsoft.AspNetCore.Mvc;
using Microsoft.DotNet.PlatformAbstractions;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.DependencyModel;
using Microsoft.Extensions.DependencyModel.Resolution;
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Reflection;
using System.Threading.Tasks;

namespace somenamespace
{
    public class MvcConfiguration : IDesignTimeMvcBuilderConfiguration
    {
        private class DirectReferenceAssemblyResolver : ICompilationAssemblyResolver
        {
            public bool TryResolveAssemblyPaths(CompilationLibrary library, List<string> assemblies)
            {
                if (!string.Equals(library.Type, "reference", StringComparison.OrdinalIgnoreCase))
                {
                    return false;
                }

                var paths = new List<string>();

                foreach (var assembly in library.Assemblies)
                {
                    var path = Path.Combine(ApplicationEnvironment.ApplicationBasePath, assembly);

                    if (!File.Exists(path))
                    {
                        return false;
                    }

                    paths.Add(path);
                }

                assemblies.AddRange(paths);

                return true;
            }
        }

        public void ConfigureMvc(IMvcBuilder builder)
        {
            // .NET Core SDK v1 does not pick up reference assemblies so
            // they have to be added for Razor manually. Resolved for
            // SDK v2 by https://github.com/dotnet/sdk/pull/876 OR SO WE THOUGHT
            /*builder.AddRazorOptions(razor =>
            {
                razor.AdditionalCompilationReferences.Add(
                    MetadataReference.CreateFromFile(
                        typeof(PdfHttpHandler).Assembly.Location));
            });*/

            // .NET Core SDK v2 does not resolve reference assemblies' paths
            // at all, so we have to hack around with reflection
            typeof(CompilationLibrary)
                .GetTypeInfo()
                .GetDeclaredField("<DefaultResolver>k__BackingField")
                .SetValue(null, new CompositeCompilationAssemblyResolver(new ICompilationAssemblyResolver[]
                {
                    new DirectReferenceAssemblyResolver(),
                    new AppBaseCompilationAssemblyResolver(),
                    new ReferenceAssemblyPathResolver(),
                    new PackageCompilationAssemblyResolver(),
                }));
        }
    }
}

and this (it's fixing compilation errors)

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Reflection.PortableExecutable;
using Microsoft.AspNetCore.Mvc.ApplicationParts;
using Microsoft.CodeAnalysis;
using Microsoft.Extensions.DependencyModel;
using Microsoft.AspNetCore.Mvc.Razor.Compilation;

namespace somenamespace
{
    public class ReferencesMetadataReferenceFeatureProvider : IApplicationFeatureProvider<MetadataReferenceFeature>
    {
        public void PopulateFeature(IEnumerable<ApplicationPart> parts, MetadataReferenceFeature feature)
        {
            var libraryPaths = new HashSet<string>(StringComparer.OrdinalIgnoreCase);
            foreach (var assemblyPart in parts.OfType<AssemblyPart>())
            {
                var dependencyContext = DependencyContext.Load(assemblyPart.Assembly);
                if (dependencyContext != null)
                {
                    foreach (var library in dependencyContext.CompileLibraries)
                    {
                        if (string.Equals("reference", library.Type, StringComparison.OrdinalIgnoreCase))
                        {
                            foreach (var libraryAssembly in library.Assemblies)
                            {
                                libraryPaths.Add(Path.Combine(AppDomain.CurrentDomain.BaseDirectory, libraryAssembly));
                            }
                        }
                        else
                        {
                            foreach (var path in library.ResolveReferencePaths())
                            {
                                libraryPaths.Add(path);
                            }
                        }
                    }
                }
                else
                {
                    libraryPaths.Add(assemblyPart.Assembly.Location);
                }
            }

            foreach (var path in libraryPaths)
            {
                feature.MetadataReferences.Add(CreateMetadataReference(path));
            }
        }

        private static MetadataReference CreateMetadataReference(string path)
        {
            using (var stream = File.OpenRead(path))
            {
                var moduleMetadata = ModuleMetadata.CreateFromStream(stream, PEStreamOptions.PrefetchMetadata);
                var assemblyMetadata = AssemblyMetadata.Create(moduleMetadata);

                return assemblyMetadata.GetReference(filePath: path);
            }
        }
    }
}

also change addMVC to this

//workaround https://github.com/dotnet/core-setup/issues/2981 will be fixed in 2.0.1
            services.AddMvc().ConfigureApplicationPartManager(manager =>
            {
                var oldMetadataReferenceFeatureProvider = manager.FeatureProviders.First(f => f is MetadataReferenceFeatureProvider);
                manager.FeatureProviders.Remove(oldMetadataReferenceFeatureProvider);
                manager.FeatureProviders.Add(new ReferencesMetadataReferenceFeatureProvider());
            });

and you will able to use dll in your view

also you have second way is disable razor precompilation here example Deleting PrecompiledViews.dll from ASP.Net Core 2 API

来源：https://stackoverflow.com/questions/47170668/cannot-find-compilation-library-location-for-package-enc-dll-error-occur-ne