Not sure why interviewer thought to mention SQL Server in specific.With ADO.Net, there are 2 ways to access data---Connected architecture--Disconnected architectureDataReader is example of connected architecture as it keeps conneection open untill all records are fetched. It's forward only so, you do not have access to previous items in the same connection.DataSet is an example of disconnected architecture as it gets all records at once and closes connection.Check this blog: http://helpingdotnet.blogspot.in/2011/10/connected-and-disconnected-architecture.html

Main difference is that :In connected architecture we should manually open DB connectionIn Disconnected connection maintained automatically

In connected mode All time data accessed from database. But in disconnected mode all the data stored on browser

if we use connected mode then all time data accessed from server this decreases the performance &if we use disconnected mode then first time data accessed from server and stored at client system cache this increases the performance but decreases security