ADO.NET is a group of classes used   to access and manipulate the data from the database servers. In short,   ADO.NET =   legacy Microsoft ActiveX Data Objects + Microsoft .NET framework. ADO.NET is an upgraded version of classic ADO with support from .NET framework features i.e. CLR Integration, Memory Management, etc. ADO.NET What is the namespace or library we need to import to work with ADO.NET? Import the below base library to invoke the ADO.NET classes. Using System. Data;  What are the main classes inside ADO.NET? 1.SqlConnection (or) OleDbConnection (or) OdbcConnection 2.SqlCommand (or) OleDbCommand (or) OdbcCommand 3.SqlDataReader (or) OleDbDataReader (or) OdbcDataReader 4.SqlDataAdapter (or) OleDbDataAdapter (or) OdbcDataAdapter 5.DataSet   What are the Connection classes in ADO.NET? The Connection classes are used to define the connection to a specific database server. ADO.NET supports three types of connection classes, i.e. 1.SqlConnection 2.OleDb