The .Net Framework includes mainly three Data Providers for ADO.NET. They are the Microsoft SQL Server Data Provider ,OLEDB Data Provider and ODBC Data provider. You can see from the following links how these Data Providers making connection to the specified data Sources.

SQL Server Connection

OLEDB Connection

ODBC Connection

The four Objects from the .Net Framework provide the functionality of Data Providers in ADO.NET. They are Connection Object, Command Object , DataReader Object and DataAdapter Object. The following link shows in details about these Objects.

Connection

Command

DataReader

DataAdapter