ADO.NET in a Nutshell

DataReader Object Overview

As with all connection-specific objects, there is a DataReader for every data provider. Here are two examples:

• System.Data.SqlClient.SqlDataReader provides forward-only, read-only access to a SQL Server database (Version 7.0 or later).

• System.Data.OleDb.OleDbDataReader provides forward-only, read-only access to a data source exposed through an OLE DB provider.

Every DataReader object implements the System.Data.IDataReader and the System.Data.IDataRecord interfaces. The IDataReader interface provides the core methods shown in Table 5-1, such as Read( ) , which retrieves a single row from the stream. The IDataRecord interface provides the indexer for the DataReader and allows you to access the column values for the current row by column name or ordinal number.

Table 5-1. IDataReader methods

Member	Description
Close( )	Closes the DataReader but not the underlying Connection. This allows you to use the Connection for another task.
GetSchemaTable( )	Retrieves a DataTable object with information about the schema for the current result set.
NextResult( )	When executing a Command that returns multiple result sets, you must use NextResult( ) to move from one result set to another. This method returns true if there are more result sets.
Read( )	Loads the next row into the DataReader. This method returns true if there are more rows left to be read.

The key to understanding the DataReader is to understand that it loads only a single row into memory at a ...