What is exactly meaning of disconnected and connected approach in ADO.NET?

In short:

• Disconnected = Make Connection , Fetch Data , Close Connection
• Connected = Make Connection , Keep Connection alive , Close Connection when close is called.

The ADO.net architecture, in which connection must be kept open till the end to retrieve and access data from database is called as connected architecture. Connected architecture is built on the these types – connection, command, datareader

The ADO.net architecture, in which connection will be kept open only till the data retrieved from database, and later can be accessed even when connection to database is closed is called as disconnected architecture. Disconnected architecture of ADO.net is built on these types – connection, dataadapter, commandbuilder and dataset and dataview.