19. Which property is used to check whether a DataReader is closed or opened?
The IsClosed property is used to check whether a DataReader is closed or opened. This property returns atrue value if a Data Reader is closed, otherwise a false value is returned.
20. Name the method that needs to be invoked on the DataAdapter control to fill the generated DataSet with data?
The Fill() method is used to fill the dataset with data.
21. What is the use of the Connection object?
The Connection object is used to connect your application to a specific data source by providing the required authentication information in connection string. The connection object is used according to the type of the data source. For example, the OleDbConnection object is used with an OLE-DB provider and the SqlConnectionobject is used with an MS SQL Server.
22. What is the use of the CommandBuilder class?
The CommandBuilder class is used to automatically update a database according to the changes made in aDataSet.
This class automatically registers itself as an event listener to the RowUpdating event. Whenever data inside a row changes, the object of the CommandBuilder class automatically generates an SQL statement and uses theSelectCommand property to commit the changes made in DataSet.
OLEDB provider in .NET Framework has the OleDbCommandBuiider class; whereas, the SQL provider has theSqlCommandBuilder class.
23. Explain the architecture of ADO.NET in brief.
AD0.NET consists of two fundamental components:
- The DataSet, which is disconnected from the data source and does not need to know where the data that it holds is retrieved from.
- The .net data provider, which allows you to connect your application to the data source and execute the SQL commands against it.
The data provider contains the Connection, Command, DataReader, and DataAdapter objects. TheConnection object provides connectivity to the database. The Command object provides access to database commands to retrieve and manipulate data in a database. The DataReader object retrieves data from the database in the readonly and forward-only mode. The DataAdapter object uses Command objects to execute SQL commands. The DataAdapter object loads the DataSet object with data and also updates changes that you have made to the data in the DataSet object back to the database.
24. Describe the disconnected architecture of ADO.NET’s data access model.
ADO.NET maintains a disconnected database access model, which means, the application never remains connected constantly to the data source. Any changes and operations done on the data are saved in a local copy (dataset) that acts as a data source. Whenever, the connection to the server is re-established, these changes are sent back to the server, in which these changes are saved in the actual database or data source.