The System.Data.SqlClient namespace contains the provider-specific ADO.NET objects used to connect to a SQL Server 7 or SQL Server 2000 database, execute a command, and transfer information to and from a DataSet . The SQL Server .NET provider is optimized for accessing the SQL Server data source protocol; it doesn't use an intermediate OLE DB provider or ODBC driver. The classes in this namespace can also be used with MSDE databases. If you need to connect to a version of SQL Server earlier than 7.0, you need to instead use the .NET OLE DB data provider.
Many types in this namespace implement a common interface from the System.Data namespace or inherit from a class in the System.Data.Common namespace. This ensures a high degree of commonality between these types and those supplied with other ADO.NET data providers. The documentation for this namespace refers to these inherited classes and implemented interfaces where appropriate, and notes any SQL Server-specific functionality. Figure 36-1 and Figure 36-2 show the types in this namespace.
Figure 36-1. The System.Data.SqlClient namespace
Figure 36-2. More types from System.Data.SqlClient