ADO.NET in a Nutshell

The SQL Server Provider

The SQL Server provider provides access to a SQL Server database (Version 7.0 or later) through the optimized Tabular Data Stream (TDS) interface (see Table A-1). To connect to the pre-7.0 version of SQL Server, use the OLE DB .NET data provider with the SQL Server OLE DB provider (SQLOLEDB). The connection-specific types are found in the System.Data.SqlClient namespace.

Table A-1. SQL Server provider classes

Interface	Implementing class
IDbConnection	SqlConnection
IDbCommand	SqlCommand
IDataParameter, IDbDataParameter	SqlParameter
IDataReader, IDataRecord	SqlDataReader
IDataAdapter, IDbDataAdapter	SqlDataAdapter
IDbTransaction	SqlTransaction

The SQL Server provider also provides .NET structures that map exactly to SQL Server types in the System.Data.SqlTypes namespace (see Table A-2). You can use SqlDataReader methods such as GetSqlMoney( ) and GetSqlDataTime( ) to retrieve values using these types (as described in Chapter 2).

Table A-2. Native SQL Server data types

SQL Server data type	Mapped .NET Type(System namespace)	Underlying .NET type(SqlTypes namespace)
Binary	Byte[]	SqlBinary
Bigint	Int64	SqlInt64
Char	String	SqlString
Datetime	DateTime	SqlDateTime
Decimal	Decimal	SqlDecimal
Float	Double	SqlDouble
Image	Byte[]	SqlBinary
Int	Int32	SqlInt32
Money	Decimal	SqlMoney
Nchar	String	SqlString
Ntext	String	SqlString
Nvarchar	String	SqlString
Numeric	Decimal	SqlDecimal
Real	Single	SqlSingle
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