ADO.NET DataReader object is used for accessing data from the data source.
The ADO.NET SqlCommand class in C# is used to store and execute the SQL statement against the SQL Server database.
SQLConnection Class of ADO.Net •It is used to establish an open connection to the SQL Server database. […]
introduction to ado.net
ADO.NET is a module of .Net Framework which is used to establish connection between application and data sources.