C# 4 and .NET 4

aDo.neT overview ❘ 819
The following table lists the classes found in the System.Data.Common namespace.
Class
DataColumnMapping
DataTableMapping
desCriPTion
Maps the name of a column from the database to the name of a column
within a DataTable.
Maps a table name from the database to a DataTable within a
DataSet.
database-specific Classes
In addition to the shared classes introduced in the previous section, ADO.NET contains a number of
database-specific classes. These classes implement a set of standard interfaces defined within the System
.Data namespace, allowing the classes to be used in a generic manner if necessary. For example, both the
SqlConnection and OleDbConnection classes derive from the DbConnection class, which implements
the IDbConnection interface. The following table lists the database-specific classes.
Classes
desCriPTion
SqlCommand, OleDbCommand, and ODBCCommand Used as wrappers for SQL statements or stored procedure
calls. Examples for the SqlCommand class are shown later
in the chapter.
SqlCommandBuilder, OleDbCommandBuilder,
and ODBCCommandBuilder
SqlConnection, OleDbConnection, and
ODBCConnection
SqlDataAdapter, OleDbDataAdapter, and
ODBCDataAdapter
SqlDataReader, OleDbDataReader, and
ODBCDataReader
SqlParameter, OleDbParameter, and
ODBCParameter
SqlTransaction, OleDbTransaction, and
ODBCTransaction
Used to generate SQL commands (such as INSERT,
UPDATE, and DELETE statements) from a SELECT
statement.
Used to connect to the database and is similar to an ADO
connection. Examples are shown later in the chapter.
Used to hold select, insert, update, and delete
commands, which are then used to populate a
DataSet and update the database. Examples of the
SqlDataAdapter are presented in this chapter.
Used as a forward-only, connected data reader. Some
examples of the SqlDataReader are shown in this
chapter.
Used to define a parameter to a stored procedure.
Examples of how to use the SqlParameter class are
shown in this chapter.
Used for a database transaction, wrapped in an object.
The most important feature of the ADO.NET classes is that they are designed to work in a disconnected
manner, which is important in today’s highly web-centric world. It is now common practice to architect a
service (such as an online bookshop) to connect to a server, retrieve some data, and then work on that data
on the client before reconnecting and passing the data back for processing. The disconnected nature of
ADO.NET enables this type of behavior.
Classic ADO 2.1 introduced the disconnected record set, which permits data to be retrieved from a
database, passed to the client for processing, and then reattached to the server. This used to be cumbersome
to use because disconnected behavior was not part of the original design. The ADO.NET classes are
different — in all but one case (the [provider]DataReader), they are designed for use offline from
the database.
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