DLR does not respect InternalsVisibleTo for anonymous types

[natemcmaster]

In full .NET, anonymous types are accessible via DLR across assembly boundaries if an InternalsVisibleTo attribute is present. This behavior is not the same in CoreCLR. Instead, a RuntimeBinderException is thrown.

Microsoft.CSharp.RuntimeBinder.RuntimeBinderException: 'object' does not contain a definition for 'xxxx'

Consider the following scenario:

In assembly ConsoleApp:

    public class Program
    {
         public static void Main()
         {
            var list = new List<object>();
            list.AddGreeting("Hello world");
            dynamic item = list[0];
            Console.WriteLine(item.Greeting); // throws in CoreCLR. Prints "Hello world" in full .NET
         }
     }

In assembly GreetingLibrary:

[assembly: InternalsVisibleTo("ConsoleApp")]

public static class ListExtension
{
    public static void AddGreeting(this List<object> source, string greeting)
    {
        source.Add(new { Greeting = greeting });
    }
}

In .NET 4.5.1, this console application will print "Hello world" but in CoreCLR this application throws an exception.

Full repro project:
test-dlr-bug-master.zip

[Eilon]

Note: This is blocking some EntityFramework scenarios.

[natemcmaster]

Fortunately there simple workaround: just don't use anonymous types if they are potentially used outside the assembly. (See dotnet/efcore#3898)

[Eilon]

@natemcmaster I would recommend avoiding using anonymous types entirely within our product codebase (in tests is fine). Anonymous types can produce many surprises.

[gkhanna79]

@jaredpar This looks like a Roslyn issue - Can you please route this?

[karelz]

The is by design - .NET Core reflection is more restrictive.