Accessing properties of anonymous/dynamic types across dll boundaries gives RuntimeBinderException

Question

In the following sample, x.propertyX works fine, whereas y.propertyX gives me a Microsoft.CSharp.RuntimeBinder.RuntimeBinderException, complaining 'propertyX' is not defined in 'object'.

The CreateDynamic method in the Program class (shown below) and the one in Class1 (not shown) are exactly the same, but Class1 is in a different project from Program. If I move Class1 into Program's project, everything works fine.

class Program
{
    public static object CreateDynamic()
    {
        return new { propertyX = "asdf" };
    }

    static void Main(string[] args)
    {
        dynamic x = CreateDynamic();
        Console.WriteLine(x.propertyX);

        dynamic y = Class1.CreateDynamic();
        Console.WriteLine(y.propertyX);

What do I need to do to make anonymous types work across dlls as dynamic types - or is that not possible?

Update: Fwiw, I figured out that I can get around that using ExpandoObjects, which I then 'cast' to dynamic, but ExpandoObjects are are not as nicely instantiable, when compared to the

new { key1 = val1, key2 = val2 }

style that anonymous types offer.

Answer 1

Anonymous types are internal to the assembly they are created in. If you have control over the source code you can make them Friend Assemblies

[assembly:InternalsVisibleTo("TheOtherAssembly")]

but there are drawbacks.