Objects That Are Found in ADO.NET

As mentioned previously, the main object that is used with ADO.NET is the DataSet object. You can see the DataSet object and its properties, methods, and additional objects in Figure 3.1.

Take a look at Table 3.1 to see a brief description of some of the objects that you will be using during this How-To.

Table 3.1. ADO.NET Data Objects That Are Used to Manipulate Data

Object	Purpose
DataSet	This object is used in conjunction with the other data controls, storing the results that are returned by commands and the data adapters. Unlike the recordset from ADO and DAO, the data set actually brings back a hierarchical view of the data. Using properties and collections in the DataSet object, you can get overall relations, individual tables, rows, and columns.
DataTable	One of the objects off of the data set, the DataTable object enables you to manipulate an individual table's worth of data. The data table is similar to the recordset object that is found in ADO.
DataView	Using this object, you can filter and sort your data, keeping various views of the data. Each data table has a default view, which is the starting data view that can be modified and stored in a separate data view.
DataRow	This object enables you to manipulate the rows of data in your data tables. This can be thought of as a cache of data that you can manipulate by adding, deleting, and modifying records. You can then accept the changes back to the recordset, where you will then run SQL statements to update data back at the server.
DataColumn	As the name suggests, you can get information at the column level by using the DataColumn object. You can get schema information as well as data using this object. For example, if you want to create a list box of names of fields, you could iterate through the DataColumn collection off a data row and retrieve all the names of the fields.
PrimaryKey	This object allows you to specify a primary key for a data table. That way, when you use the Find method of the data table, it knows which column to use.

.NET also provides classes, called data providers, to work with ADO.NET objects to provide access to data. You can see some of those objects in Figure 3.2.

In Table 3.2, you can see a brief description of some of the objects that you will be using during this How-To.

Table 3.2. .NET Data Provider Classes That Are Used to Manipulate Data

Object	Purpose
Command	Similar to the ADO Command object, this allows you to execute stored procedures in code. Unlike the ADO version, however, you can create a DataReader object using the ExecuteReader method.
Connection	This object opens a connection to the server and database with which you want to work. Unlike the ADO Connection object, the way that the connection remains open depends on the object with which you are working, such as a DataReader or DataSet object.
DataAdapter	A real workhorse, the DataAdapter object allows you to create SQL statements and fill datasets with the data. It also creates other necessary action queries, such as Insert, Update, and Delete ADO.NET command objects.
DataReader	This object creates a read-only, forward-only stream of data that allows you to quickly populate controls, such as ListBox and ComboBox controls.
Parameter	This object allows you to specify the parameter (or parameters if you use more than one) that DataAdapter objects can specify and use.

You will get a chance to see all of the items listed in the previous two tables throughout the following How-Tos.

All of the examples in this chapter can be found in the Solution called VB.NET-Chapter 3 on the Web site.