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I have learned multi-layered .NET implementation on 2002 with Duwamish microsoft sample.

Duwamish 7.1 is a multitier, distributed business-to-consumer commerce application built specifically for the Microsoft .NET platform.

this is the overview of Diwamish Layers architecture:

The application can be deployed on a single machine, in a physical two-tier (Web, database) configuration, or physical three-tier (Web, application, database) configuration.

Presentation
ASP.NET Web Forms and Server Controls
ASP.NET output caching

Business Logic
Implementation in both Visual C# and Visual Basic .NET
Business facade, business rules

Data Access
ADO.NET DataSets using SQL provider

Data
Microsoft SQL Server™ 2000 database using stored procedures

here are some related links :

Three Tier Architecture in ASP.NET
Database transactions

Architecture of Duwamish

Download Duwamish

Duwamish7 (C#)