Hey, Fred,

I'm sure others will have some good examples (I'm not familiar enough with the pet store example to say one way or another)

One piece of advice I'll throw out is that the general rules for a well-designed three-tier system are really independent of any one technology. Things like decoupling, balancing load, designing a data access layer with one way in and one way out, constructing a database and establishing business rules/business objects, what belongs in the UI and what doesn't belong in the UI...they're all things that largely transcend the language.

As for implementing them in a particular language (C#, in this case), I don't know of one good on-line site that has a complete and comprehensive example, but I'm sure others here might.

I do know that over on http://www.c-sharpcorner.com, they have some good examples on pieces of a multi-tier system (remoting, web services, data access layers, etc.) If I can think of any others, I'll let you know.

And while I don't own a copy, the .NET Mere Mortals Framework (while not free) certainly provides an infrastructure for developing n-tier. Also the author of Mere Mortals (Kevin McNeish) has a very good book (.NET for VFP Develpoers) that covers many of the things you'll face in developing n-tier. It doesn't have a complete n-tier example, but covers several of the 'pieces'

Hope that helps,
Kevin