Read the following articles: N-Tier Applications and .NET, N-Tier Applications and .NET: A Simple Example and N-Tier Applications and .NET: Achieving Isolation between DAL and BOL to understand how a typical 3-tier application looks like and how to achieve isolation between Data Access Layer and Business Object Layer. in the last article u will see that we still have tight coupling between UI and database. This is due to the fact that our Select methods are returning DataSets which contain actual database column names. This means any change to database column names is going to affect UI layer. This article by bipin joshi takes the concept one step ahead and shows how this coupling can be reduced.
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