[From SQL Server Performance]
A Data Access Layer (DAL) is an integral part in the design of any application. There are plenty of articles that discuss how we an implement a DAL using ADO.NET. Most of these have constraints in the sense that they are not generic in nature. In other words, they are not provider independent. This series of articles will discuss the implementation of a generic, i.e., a provider independent Data Access Layer in ADO.NET. The basic prerequisite to learning this article is a proper understanding of ADO.NET and good coding skills in C#. I will present the code examples in this article in C#. However with little effort, you can twist it over to VB.NET as well.
The article continues at http://sql-server-performance.com/articles/asp_ado/Generic_Data_Access_Layer_Part1_p1.aspx