I believe you can only use collection in vb.net instead of c#. C# has Collection, but you have to specify the type, for example Collection<yourclass>, and this structure cannot be used by VB6!
In vb.net, you can create a generic list with a property is Collection, then you can add any object to this collection and comsume it in VB6
Public Class GenericList
Private _list As New Collection
Public Property List() As Collection
Get
Return _list
End Get
Set(value As Collection)
_list = value
End Set
End Property
End Class