101 Microsoft® Visual Basic® .NET Applications

Application #21. Build a Three-Tier Data Form

For most business applications, a well-known “best practice” is to organize your code into three tiers. Although there are differences of opinion about how a tier is defined and what goes where exactly, the typical model is as follows:

• An upper or presentation tier for the user-interface code

• A middle or business tier to house business rules and data-access logic

• A lower tier that contains the data storage—for example, a database

A three-tier architecture has a number of advantages, such as scalability and code reuse. For example, when the data-access logic is not tightly coupled with the presentation tier, it can easily be reused to serve many types of user interfaces, from a rich desktop client to ...