Bug description

In Visual Studio extensibility host process, we have a model where process has a single instance of MessagePack assembly but each extension is hosted under a different AssemblyLoadContext. In cases where 2 extensions have the same assembly with message pack compatible types, and process has 2 instances of the assembly load under different contexts the dynamic resolver will fail to work due to type equivalence issues.

Per our chat with @AArnott, this is happening because there is a single instance of DynamicUnionResolver assembly in the context of MessagePack assembly and a limitation is that an assembly in .net can't have a reference to 2 instances of the same assembly name. So we need to consider having a different DynamicUnionResolver assembly per load context (and similarly for other dynamic resolver assemblies too).

Repro steps

• Create an assembly with a message pack object that has union attribute.

• Load message pack in a .net core app in the default load context.

• Load the test assembly twice under different load contexts and try to serialize an instance of the object.

• Runtime: (e.g. .NET Framework, .NET Core, Unity, mono, etc.) .Net Core

Additional context

Add any other context about the problem here.