This chapter explains how to perform database programming in an object-oriented way. There are several techniques (patterns) we can use to make a VB.NET/ADO.NET program object-oriented. Many of these techniques were first discussed (though not necessarily first used) in Martin Fowler's book Patterns of Enterprise Application Architecture (Fowler 2003). This chapter will distill some of the patterns he presents into working code that a VB.NET programmer will recognize, especially a programmer who now understands OOP. First, though, we'll provide you with an overview of how to use ADO.NET to access data stored in a database.

AN OVERVIEW OF ADO.NET

ActiveX Data Objects.NET (ADO.NET) is an object-oriented database API that allows a programmer to use one set of classes to access many different types of databases.

ADO.NET Objects

ADO.NET consists of a set of classes that encapsulate the behavior of the different aspects of a database. These classes include objects that represent the database, individual tables, columns within tables, and rows in tables. There are also specialized objects for making database connections and database commands.

The following list highlights these objects

• DataSet represents a subset of a database and is a parent object to many of the other objects used in ADO.NET.

• DataTable is used to work with the contents of a single table.

• DataColumn is used to represent each column in a table.

• DataRow represents a row of data from a table. Row data are retrieved from the Rows collection of a DataTable object.

• DataAdapter is used as a bridge between a DataTable object and the physical data source, or database, the program is using.

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