DataReader class. Many data operations only let
developers to read a string of data. DataReader
object promises developers to get the result from
the select sentence of Command object.
Considering of performance factor, the returned
data from DataReader are all quickly and only
“forward” data flow. This means developers only
can follow certain sequence to get data from data
flow. This is good for speed. But if developers
want to operate data, the best way is to use
DataSet.