Beginning Web Development, Silverlight, and ASP.NET AJAX

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CHAPTER 4 ■ DATA BINDING WITH ASP.NET
of maintaining state between the tiers of your application can be much higher, as you
may be passing large amounts of data (sometimes referred to as data sets) between them.
Thus, ADO.NET offers a disconnected model that enables you to access data from
another tier, disconnect from that tier (thus breaking state), and access that data locally.
To prevent data from being corrupted, ADO.NET provides the means for syncing back up
with the data store when your transaction is complete, as well as locking mechanisms to
prevent other processes from affecting the data while your application is holding it in a
disconnected state.
At the heart of the disconnected model is XML. ADO.NET was designed with the
XML classes of the .NET Framework in mind, and at the core of this is the DataSet object,
which you’ll undoubtedly encounter if you continue writing ADO.NET-based applications.
(It’s also used under the covers when controls are automatically bound to a
database, although that’s not obvious at a casual glance.)
Using ADO.NET
You use a .NET data provider to connect to the data store. A provider is one or more
classes that give you programmatic access to a database, providing methods that enable
you to read or update data stored in the supported data store. The main classes that you’ll
use when using a data provider to connect to databases are as follows:
Connection: As its name suggests, the Connection class is used to make and manage
the connection with the database.
Command: You use Command to create and execute Structured Query Language (SQL)
statements against your database, or to access stored procedures already on the
database and execute them.
DataReader: When you want to access data in a read-only manner, moving forward
through the data as you read, this class provides a lightweight, fast component that
achieves this.
DataAdapter: The DataAdapter class is used to facilitate the communication between
the disconnected DataSet and the data store. It fills the DataSet with data and provides
the methods to apply changes to the data stored within the data store based
on any modifications made within the (disconnected) DataSet.
DataSet: The DataSet is a disconnected representation of all or part of a database. It is
much more sophisticated than something like a recordset or table because it can
support a collection of tables, relationships, constraints, and more.
ADO.NET supplies you with a number of built-in providers, including a SQL Server
provider that is optimized for SQL Server. This includes all of the preceding classes