ADO.NET components access the database in two ways: in a connected way and in a disconnected way. In the connected access method, we deal with synchronous communication with a database instance, sending any instances of data definition language (DDL) or data manipulation language (DML). In the disconnected access method, we store a pseudo-copy of data and schema of any table locally, with the ability to save changes (if any) asynchronously.

In the end, any time we deal with ADO.NET, as with low level classes, or with high level OR/M classes, we always produce some SQL statement. This statement may be the result of an OR/M data provider that translate object-oriented code in SQL code or may be the result of our direct text entry like when we write the SQL by ourselves or like when we simply invoke a stored procedure (an SQL statement stored on the database itself). Eventual parameters may be used to parameterize the SQL execution. Never concatenate strings to produce an...