Ais used to perform a forward-only (sequential) access of the data in the data source while a is used to populate a dataset and updates the database. a.connection, data adapterb. data reader, commandc. data adapter, data readerd. data reader, data adapter



d. Data reader, Data Adapter

Explanation:

Data Reader statements are used to sequentially read streams of data from a database into a program.

It provides an easy way to read data from a data source or database in a one way direction.

Data Adapter:

DataAdapter is an object used in a disconnected data environment and can be seen as a link between a data sourc and this disconnected data class.

It clearly identifies commands, brings data from the database and then populates these data in the data set.

An example of their usage in Microsoft Visual C# (winforms) is

SqlConnection connect = new SqlConnection ("connection string");

connect.Open();

SqlCommand command = new SqlCommand("SQL Query", connect);

SqlDataReader reader = command.ExecuteReader();

Data Adapter

SqlConnection connect = new SqlConnection ("connection string");

connect.Open();

SqlDataAdapter adapter = new SqlDataAdapter("SQL Query", connect);

DataSet dset = new DataSet();

adapter.Fill(dset);