What are alternatives to generic collections for COM Interop?

After some more research and trial-and-error, I think I found a solution by using System.Collections.ArrayList. However, this does not work with getting a value by index. To do so, I created a new class ComArrayList that inherits from ArrayList and adds new methods GetByIndex and SetByIndex.

COM Interop compatible collection:

public class ComArrayList : System.Collections.ArrayList {
    public virtual object GetByIndex(int index) {
        return base[index];

    public virtual void SetByIndex(int index, object value) {
        base[index] = value;

Updated .NET component MyLibrary.GetDepartments:

public ComArrayList GetDepartments() {
    // return a list of Departments from the database

Updated ASP:

<h1>The third department</h1>
<%= departments.GetByIndex(2).Name %>

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