Tài liệu Developing a Universal Data Access Layer leveraging ADO.NET, C# and Factory Design Pattern

Ideally, every software application will access the data from all possible data sources in the same manner. Every
application will be able to manipulate data in every possible way. But we do not live in a perfect world. There are
limitations on how we can or cannot access certain types of data. In the past few years Microsoft's ActiveX Data
Object (ADO) has revolutionized data access mechanism. With the arrival of .NET, comes ADO.NET, which truly is
the next generation of the ADO data species. In this article, readers will learn how to build a thin universal data
access layer at the top of ADO.NET using Design Patterns and .NET Framework. This component layer, which will
be based on ADO.NET, will provide access to OLE DB Managed Providers as well as SQL Server Managed Providers
through a single interface. It will be extensible so that in the future we can add access to other Managed providers
when they become available.
This article does not require a prior knowledge of Design Patterns. However, familiarity with Object Oriented
Design and Analysis techniques is recommended. A brief overview of Design Patterns is covered later in the
article. The discussion on n-tier (Presentation Tier, Business Tier, Data Tier) design and architecture is beyond the
scope of this article. It assumes that readers have some familiarity with n-tier design.