See the example below.
I have a .Net class Customer which implements an interface ICustomer, and
which is stored in a collection CustomerCollection.
Both CustomerCollection and ICustomer are exposed to COM (ComVisible = true)
My Customer object is *not* exposed to COM (ComVisible = false), mainly
because I don't want my COM clients to be able to instantiate Customer
objects - only get them returned by methods of another class (in this example
returned by CustomerCollection's indexer).

When I attempt to access this from VB6, everything works fine, except that I
can't iterate through my CustomerCollection using "for each":

   Dim col As VB6Test.CustomerCollection
   Dim cust As VB6Test.ICustomer
   Set col = New VB6Test.CustomerCollection
   
   For Each cust In col
       Debug.Print cust.Name
   Next cust

The above VB6 code raises an error 424 'Object required' at the line "For
Each...".

Now if I modify my .NET Customer class to set ComVisible = true, the VB6
code works fine.  But I don't want this class to be visible to Com objects.

Can anyone explain this behavior and suggest a workaround?

Thanks,
Joe
============= ICustomer interface ===================
[
ComVisible(true),
GuidAttribute("16870d0c-213c-11da-9422-000bdb57d597")
]
public interface ICustomer
{
    string Name { get; set; }
}
============= Customer class ===================
[
ComVisible(false),
GuidAttribute("16870d0a-213c-11da-9422-000bdb57d597"),
]
public class Customer : ICustomer
{
    public Customer()
    {
    }

    public Customer(string name)
    {
        Name = name;
    }

    public string Name
    {
        get { return _name == null ? "" : _name; }
        set { _name = value; }
    }
    private string _name;
}
============= CustomerCollection class ===================
[
ComVisible(true),
GuidAttribute("16870d0b-213c-11da-9422-000bdb57d597"),
ClassInterface(ClassInterfaceType.AutoDual)
]
public class CustomerCollection : CollectionBase
{
    public CustomerCollection()
    {
        ((IList)this).Add(new Customer("Customer1"));
        ((IList)this).Add(new Customer("Customer2"));
    }

    public ICustomer this[int index]
    {
        get { return (ICustomer) InnerList[index]; }
        set { InnerList[index] = value; }
    }

}