The .Net Framework includes mainly three Data Providers for ADO.NET. The Microsoft SQL Server , OLEDB and ODBC are the main Data Providers included in the .Net Framework. You can see from the following links how these Data Providers making connection to the 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 Connection Object provides physical connection to the Data Source. The Command Object uses to perform SQL statement or stored procedure to be executed at the Data Source. The DataReader Object is a stream-based , forward-only, read-only retrieval of query results from the Data Source, which do not update the data. Finally the DataAdapter Object , which populate a Dataset Object with results from a Data Source . The following link shows in details about these Objects.

Connection

Command

DataReader

DataAdapter