Creating robust, large-scale n-tier applications isn't particularly easy if
you're using ASP Classic and VB6. You implement the business layer as
ActiveX components (EXE or DLL COM/DCOM objects) that have to be
installed/registered where they are accessible to IIS. Your ASP pages or
application can then access them as objects through direct instances and/or
MTS. Frankly, it's a pain.
On the other hand, if you're using ASP.Net and VB.Net, it is far less
complicated. You can implement your business logic as Web Services, which
are considerably more flexible and maintainable. There is a ton of
information on the MSDN site about the advantages of switching to .Net, so I
won't go into the details here.
If your application has only relatively modest business logic, it is also
possible for you to create n-tier applications using just ASP Classic on IIS
5 or 6. You can create classes in script (similar to how you would in VB6)
that encapsulate your business logic and use <!-- include --> directives to
incorporate them in your other pages. This is quite helpful for isolating
business logic from the UI for simple objects like "Person" or
"OrderDetail". However, since ASP Classic is stateless, IIS has to recreate
your objects on every invocation. This means your app's performance
probably won't scale well if it has lots of concurrent users or involves
complex objects.
My recommendation is that you go with the .Net environment.
Alan
