Interview Questions on ADO.NET

Interview questions on ADO.NET

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1. What is ADO.NET?
ADO.NET is an integral part of .Net Framework, providing access to relational, XML, application data.
2. What are the data providers available in .net to connect to database?
System.Data.SqlClient: It describes a collection of classes used to access a SQL Server database. System.Data.OleDb: It describes a collection of classes used to access an OleDb data source. (Microsoft Access, MySQL, Informix, DB2, Oracle.. It uses OleDB drivers to connect to data source) System.Data.Odbc: It describes a collection of classes that are used to access a ODBC data source. (We can connect any relation database which supports odbc drivers). System.Data.OracleClient: It describes a collection of classes that are used to connect Oracle Database.
3. List all the steps to access data base using ADO.Net?
Create Connection Create connection to data source; here I am using sql connection. SQLConnection con= new SQLConnection(“datasource=localhost;database=Northwind; Integrated Security=true”) Create command SQLCommand cmd = new SQLCommand(“select * from Products”,con); Execute command Use either connected/disconnected architecture, Here I am using connected data model using DataReader. SqlDataReader reader; Con.open(); reader = cmd.ExecuteReader(); Close connection Finally close the connection. Con.Close();
4. What is the difference between OleDb data provider and SqlClient?
SqlClient provides classes that are highly optimized to connect sql server using .Net. SqlClient data provider is faster than any other data provider in Ado.Net. It is faster because it connect sql data source directly using native library.
5. What is the use of Connection object?
They are used to connect a data to a command object. SqlConnection: used to connect Sql Server. OleDbConnection: used to connect with OLE-DB provider. OdbcConnection: is used to connect with data sources with ODBC provider.
6. What is the use of Command object?
Command object is used to connect connection object to DataReader or DataSet, to execute query against data source.
7. What are the methods provided by the command object?
ExecuteNonQuery: Executes the command defined in the CommandText property against the connection defined in the Connection property for a query that does not return any rows (an UPDATE, DELETE or INSERT).Returns an Integer indicating the number of rows affected by the query. ExecuteReader: Executes the command defined in the CommandText property against the connection defined in the Connection property. Returns a "reader" object that is connected to the resulting rowset within the database, allowing the rows to be retrieved. ExecuteScalar: Executes the command defined in the CommandText property against the connection defined in the Connection property. Returns only a single value (effectively the first column of the first row of the resulting rowset). Any other returned columns and rows are discarded
8. What is the use of DataAdapter?
DataAdapter objects can connect one or more command objects to DataSet. They provide login that gets the data from the datastore and populates the tables in the DataSet,or pushes the changes in the DataSet back into the data store.
9. What is the difference between DataReader and DataAdapter?
DataReader Vs DataAdapter. DataReader provde read only and forward only data access. DataReader can increase application performance and reduce system overhead. DataReader is connection oriented where as Data Adapter is disconnected. DataReader we have to open and close connection explicitly where as if we use DataAdapter the connection is automatically opened and closed.
10. Will the connection be closed, if the SqlConnection object goes out of scope?
No, you must explicitly close the connection by calling Close or Dispose.
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