How to return an array of .NET objects via a COM method

I have a .NET assembly. It happens to be written in C++/CLI. I am exposing a few objects via COM. Everything is working fine, but I cannot for the life of me figure out how to return an array of my own objects from a method. Every time I do, I get a type mismatch error at runtime. I can return an array of ints or strings just fine.

Here is my main class

[Guid("7E7E69DD-blahblah")]
[ClassInterface(ClassInterfaceType::None)]
[ComVisible(true)]
public ref class Foo sealed : IFoo
{
public:
    virtual array<IBar^>^ GetStuff();
}

[Guid("21EC1AAA-blahblah")]
[InterfaceType(ComInterfaceType::InterfaceIsIDispatch)]
[ComVisible(true)]  
public interface class IFoo
{
public:
    virtual array<IBar^>^ GetStuff()
    {
        // For simplicity, return an empty array for now.
        return gcnew array<IBar^>(0);
    }
};

Here is the class I am returning

[Guid("43A37BD4-blahblah")]
[InterfaceType(ComInterfaceType::InterfaceIsIDispatch)]
[ComVisible(true)]  
public interface class IBar
{
    // Completely empty class, just for testing.  
    //In real life, I would like to return two strings and an int.
};

[Guid("634708AF-blahblah")]
[ClassInterface(ClassInterfaceType::None)]
[ComVisible(true)]
[Serializable]
public ref class Bar : IBar
{
};

This is my (native) C++ code that calls it:

MyNamespace::IFooPtr session(__uuidof(MyNamespace::Foo));
// For simplicity, don't even check the return.
session->GetStuff();

Calling GetStuff() gets me a _com_error 0x80020005 (DISP_E_TYPEMISMATCH). I can tell my method is being called correctly, it's just that when .NET/COM goes to marshall the return, it chokes. As I said, it works fine with arrays of ints or strings. What do I have to do to my class to allow it to be returned in an array?

As it happens, my class will only contain a couple of strings and an int (no methods), if that makes it any easier. Obviously I've tried returning a non-empty array and classes that actually contain some data, this is just the simplest case that illustrates the problem.

You need to implement IDispatch and the Enumerator method

public ref class FooCollection{
[DispId(-4)]
public IEnumerator^ GetEnumerator()
{
//...
}
}