What is the namespace in which .NET have the data functionality classes?
System.data :
This namespace contains the basic objects used for accessing & storing relational data, like DataTable,DataSet, and DataRelation. Each of these is independent of the type of the data source and the way we connect to it.
System.Data.OleDB :
This namespace contains the objects that we use to connect to a data source via an OLE-DB provider, like the OleDbCommand, OleDbConnection, etc. These objects inherit from the common base classes,& so have the similar methods,properties, and events as the SqlClient equivalents.
System.Data.SqlClient :
This namespace contains the objects that we use to connect the data source via the Tabular Data Stream (TDS) interface of the Microsoft SQL Server . This can normally give better performance as it removes some of the intermediate layers required by an OLE-DB connection.
System.XML
This namespace Contains the basic objects needed to create, store, read, write, and for manipulating XML documents according to W3C recommendations.