C# dll export System.Data.DataTable to VBA Excel

I would like to export a complex data type to VBA from a C# .dll. Such as returning the data type: "System.Data.DataTable" to a VBA sub routine.

Minimal working example (MWE) below:

// C# .dll Code:
using System;
using System.Data;              // So I can use DataTable as a type.  
using System.Runtime.InteropServices;       // Library required to allow early binding and hence gets intellisense working in VBA. 
                                            // So, it is required for "ClassInterface" and "ComDefaultInterface".

namespace ClassLibrary1
{
[ClassInterface(ClassInterfaceType.AutoDual)]       // Used to expose the class to VBA.
    public class Class1
    {
        public DataTable Test()
        {
            DataTable dtResults = new DataTable("PortfolioResults");

            dtResults.Columns.Add("Date");
            dtResults.Columns.Add("Price");
            dtResults.Rows.Add(DateTime.Today, 100.52);

            return dtResults;
        }
    }
}

The VBA code calls the method "Test" and would like to receive the 'DataTable' datatype from C#:

Option Explicit

Private Sub TestDotNetCall()
    Dim testClass As New ClassLibrary1.Class1

    Dim Results As DataTable
    Results = testClass.Test
End Sub

VBA gives me the error message "Object variable of with block variable not set".

Note: I understand there is a "Microsoft.Office.Interop.Excel.DataTable object". But casting System.Data.DataTable to the Excel kind doesn't appear allowed.

ie.

using Interop_Excel = Microsoft.Office.Interop.Excel;   // Library is required to allow Excel worksheet cells to talk to the C# COM add-in.

return (Interop_Excel.DataTable) dtResults;

VBA error message is now "Class does not support Automation or does not support expected interface".

What am I missing? How can I get such complicated types into VBA?