Visual Basic

'---------------- Test.vb ------------------------------------------------------
Imports SHDocVw

Module Test

    Public Class clsTest
        Public HWND As Long
        '
        ' Omitted additional members goes here.
        '
    End Class

    Public Sub doSomething(ByRef c() As clsTest)
        Dim i As Integer
        Dim ieCollection() As InternetExplorer = Nothing

        '
        ' Omitted code that populates ieCollection goes here.
        '

        i = 0
        For Each ie As InternetExplorer In ieCollection

            ' [Insert #1]

            c(i).HWND = ie.HWND

            i += 1
        Next
    End Sub

End Module
'---------------- End of Test.vb -----------------------------------------------


'---------------- Main.vb ------------------------------------------------------
Module Main
    Private Class clsTestExtended
        Inherits Test.clsTest

        Public strParam1 As String
        Public strParam2 As String
    End Class

    Public Sub main()
        Dim ce() As clsTestExtended = Nothing ' [Change #1]

        ' [Insert #2]

        Test.doSomething(ce)

        For Each c As clsTestExtended In ce
            c.strParam1 = ""
            c.strParam2 = ""
        Next

    End Sub
End Module
'---------------- End of Main.vb -----------------------------------------------

If c Is Nothing Then
	ReDim c(0)
Else
	ReDim Preserve c(i)
End If
c(i) = New clsTest

Unable to cast object of type 'clsTest[]' to type 'clsTestExtended[]'

Dim ce(1) As clsTestExtended

ce(0) = New clsTestExtended
ce(1) = New clsTestExtended