.Net Standard 4.7.1 Could not load System.Private.CoreLib during serialization

Question

I'm working on migrating most of my project to .Net Standard 2.0.

Last part of the project in .net standard 4.7.1 is a WCF front end. This executable communicate with a .net core application throught a library Akka.net by ClientServiceReceptionist.

Network communication between application by akka.net work. Except when an it try to serialize a ReadOnlyCollection.

In this case the system try to load a "System.Private.CoreLib.dll" that is not available.

I readed many issues with .net 4.6 using .net standard 2.0 libraries that must have been corrected in 4.7.1. I pass from package.config to PackageReference.

I tryed to used NewtonSoft as a serializer in place of Hyperion without progress.

Does anyone have an idea, a solution ?

Edit : 07-05-2018

The issue is throw in the WCF Entry Points when i sent a ClusterClient.Send object throught the ClusterClientReceptionist.

The object sent contains only boolean, string, Guid and array of string properties.

Edit 08-05-2018

The object sent look like this :

{
  (string) "Path": "/user/ProcessOrderWorkflow",
  "Message": {
    "Order": {
      "Data": {
        (string)"Sentence": "i love my name",
        "Options": {
            (boolean)"Simplify" : true,
            (IReadOnlyCollection<string>) LanguageAffinity : [ "FR", "EN" ]
        }
      },
      "OrderQuery": {
        "Verb": {
          (string)"Verb": "Extract"
        },
        "Arguments": [
          {
            (string)"Argument": "Sentence"
          },
          {
            (string)"Argument": "Meaning"
          }
        ]
      },
      (Guid)"ProcessId": "0bfef4a5-c8a4-4816-81d1-6f7bf1477f65"
    },
    (string)"ReturnTypeFullName": "Viki.Api.Server.Data.SentenceMeaningMsg,, Viki.Api.Server.Data, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null"
  },
  (boolean)"LocalAffinity": false
}

Each of the object used in the hierachi is builded using the constructor. All the properties are in readonly.

I tryed to serialize and deserialize the result on the WCF part before it's sent and it works.

var serializer = this._system.Serialization.FindSerializerFor(result);
var bytes = serializer.ToBinary(result);
var data = serializer.FromBinary(bytes, result.GetType());

The strange think is that it try to deserialize the object in the WCF part where it is sent and not in the LightHouse where the element should be received and transfert to a agent for processing.

Answer 1

So this is what I thought the issue might be... The problem is that transmitting serialized content between a .NET Core application and a .NET Framework application using a polymorphic serializer like JSON.NET or Hyperion is an unsupported operation in Akka.NET at least, but also in any other runtime where the users uses CLR types as the wire format of the messages.

A brief explanation as to why we don't support this in Akka.NET, from the v1.3.0 release notes:

As a side note: Akka.NET on .NET 4.5 is not wire compatible with Akka.NET on .NET Core; this is due to fundamental changes made to the base types in the CLR on .NET Core. It's a common problem facing many different serializers and networking libraries in .NET at the moment. You can use a X-plat serializer we've developed here: #2947 - please comment on that thread if you're considering building hybrid .NET and .NET Core clusters.

The "fundamental changes" in this case being that the namespaces for types like string are different on .NET 4.* and .NET Core, thus a polymorphic serializer that doesn't account for those differences will throw this type of exception.

We do have a workaround available here if you'd like to use it:

https://github.com/akkadotnet/akka.net/pull/2947

You'll need to register that serializer compat layer with JSON.NET inside Lighthouse and your .NET 4.7.1 apps.

Answer 2

This is a top result for request "Could not load System.Private.CoreLib" so I post the workaround for ASP.NET Core APIs and .NET clients.

If json serializer type handling set to auto

settings.TypeNameHandling = TypeNameHandling.Auto;

serializer will include type information for polymorphic types. After migration to .NET Core some clients reported exception and the response body contained following type descriptor:

"$type":"System.String[], System.Private.CoreLib"

In the API model property type was defined as IEnumerable<string> which forced serializer to include actual type for an Array. The solution was to replace IEnumerable<string> with string[] or any other concrete type which allowed serializer to omit the type descriptor.

If the above does not work, for instance when you use Dictionary<string, object> you can implement custom SerializationBinder:

public class NetCoreSerializationBinder : DefaultSerializationBinder
{
    private static readonly Regex regex = new Regex(
        @"System\.Private\.CoreLib(, Version=[\d\.]+)?(, Culture=[\w-]+)(, PublicKeyToken=[\w\d]+)?");

    private static readonly ConcurrentDictionary<Type, (string assembly, string type)> cache =
        new ConcurrentDictionary<Type, (string, string)>();

    public override void BindToName(Type serializedType, out string assemblyName, out string typeName)
    {
        base.BindToName(serializedType, out assemblyName, out typeName);

        if (cache.TryGetValue(serializedType, out var name))
        {
            assemblyName = name.assembly;
            typeName = name.type;
        }
        else
        {
        if (assemblyName.AsSpan().Contains("System.Private.CoreLib".AsSpan(), StringComparison.OrdinalIgnoreCase))
            assemblyName = regex.Replace(assemblyName, "mscorlib");

        if (typeName.AsSpan().Contains("System.Private.CoreLib".AsSpan(), StringComparison.OrdinalIgnoreCase))
            typeName = regex.Replace(typeName, "mscorlib");    
            cache.TryAdd(serializedType, (assemblyName, typeName));
        }
    }
}

And register it in JsonSerializerSettings:

settings.SerializationBinder = new NetCoreSerializationBinder();

Note: .AsSpan() for string comparison was added for backwards compatibility with .NET Framework. It doesn't harm, but not required for .NET Core 3.1+, feel free to drop it.

Answer 3

If this issue happens during deserialization in .NET Framework application and you can't do anything about the JSON you receive, then you can extend DefaultSerializationBinder and use it in JsonSerializerSettings to deserialize JSON generated by .NET Core application:

internal sealed class DotNetCompatibleSerializationBinder : DefaultSerializationBinder
{
    private const string CoreLibAssembly = "System.Private.CoreLib";
    private const string MscorlibAssembly = "mscorlib";

    public override Type BindToType(string assemblyName, string typeName)
    {
        if (assemblyName == CoreLibAssembly)
        {
            assemblyName = MscorlibAssembly;
            typeName = typeName.Replace(CoreLibAssembly, MscorlibAssembly);
        }

        return base.BindToType(assemblyName, typeName);
    }
}

and then:

var settings = new JsonSerializerSettings()
{
    SerializationBinder = new DotNetCompatibleSerializationBinder()
};

Answer 4

for the base Type try to use

serializer.TypeNameHandling = TypeNameHandling.Auto

can ignore the System.Private.CoreLib namespace in Json