ODBC

ODBC provides interface to many different kind of databases (access, sql, oracle), and it is independent of languages.

Microsoft ODBC comes by default in windows.

C# dataccess utilizing ODBC

OdbcConnection class provides generic interfaces for all kind of databases. Pitfall is that the sql syntax of Access, Oracle, Sql may not be similar. Best approach in this circumstance is to use stored procs. In addition to the databases, this also provides access to xls, csv, and txt files. However, for files deleting and updating records is not supported. The connection string can be defined in the application or in the Data Source (ODBC) Administrator application that is in the Control Panel Administrative tools. Here you define the connection string to the data. You provide DSN=dsn_name in the application and it determines the source.

Microsoft Enterprise Library:

I believe Microsoft enterprise library dataaccess is better than ODBC. It allows the user to utilize the ODBC sources as well the sources directly.