Interview Questions Part IV

1.Advantage of ADO.Net?

ADO.NET Does Not Depend On Continuously Live Connections.
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Database Interactions Are Performed Using Data Commands.
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Data Can Be Cached in Datasets.
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Datasets Are Independent of Data Sources.
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Data Is Persisted as XML.
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Schemas Define Data Structures

2.How would u connect to database using .NET?

SqlConnection nwindConn = new SqlConnection("Data Source=localhost; Integrated
Security=SSPI;" + "Initial Catalog=northwind");nwindConn.Open();

3.What are relation objects in dataset and how & where to use them?

In a DataSet that contains multiple DataTable objects, you can use DataRelation objects
to relate one table to another, to navigate through the tables, and to return child or parent
rows from a related table. Adding a DataRelation to a DataSet adds, by default, a
UniqueConstraint to the parent table and a ForeignKeyConstraint to the child table.

4.Difference between OLEDB Provider and SqlClient ?

SQLClient .NET classes are highly optimized for the .net / sqlserver combination and
achieve optimal results. The SqlClient data provider is fast. It's faster than the Oracle
provider, and faster than accessing database via the OleDb layer. It's faster because it
accesses the native library (which automatically gives you better performance), and it
was written with lots of help from the SQL Server team.

5.What are the different namespaces used in the project to connect the database?

What data providers available in .net to connect to database?
System.Data.OleDb – classes that make up the .NET Framework Data Provider for OLE
DB-compatible data sources. These classes allow you to connect to an OLE DB data
source, execute commands against the source, and read the results.
System.Data.SqlClient – classes that make up the .NET Framework Data Provider for
SQL Server, which allows you to connect to SQL Server 7.0, execute commands, and
read results. The System.Data.SqlClient namespace is similar to the System.Data.OleDb
namespace, but is optimized for access to SQL Server 7.0 and later.
System.Data.Odbc - classes that make up the .NET Framework Data Provider for
ODBC. These classes allow you to access ODBC data source in the managed space.
System.Data.OracleClient - classes that make up the .NET Framework Data Provider for
Oracle. These classes allow you to access an Oracle data source in the managed space.

6.Difference between DataReader and DataAdapter / DataSet and DataAdapter?

You can use the ADO.NET DataReader to retrieve a read-only, forward-only stream of
data from a database. Using the DataReader can increase application performance and
reduce system overhead because only one row at a time is ever in memory.After creating
an instance of the Command object, you create a DataReader by calling
Command.ExecuteReader to retrieve rows from a data source, as shown in the following
example.SqlDataReader myReader = myCommand.ExecuteReader();You use the Read
method of the DataReader object to obtain a row from the results of the query.while
(myReader.Read()) Console.WriteLine("\t{0}\t{1}", myReader.GetInt32(0),
myReader.GetString(1));myReader.Close();The DataSet is a memory-resident
representation of data that provides a consistent relational programming model regardless
of the data source. It can be used with multiple and differing data sources, used with
XML data, or used to manage data local to the application. The DataSet represents a
complete set of data including related tables, constraints, and relationships among the
tables. The methods and objects in a DataSet are consistent with those in the relational
database model. The DataSet can also persist and reload its contents as XML and its
schema as XML Schema definition language (XSD) schema.The DataAdapter serves as a
bridge between a DataSet and a data source for retrieving and saving data. The
DataAdapter provides this bridge by mapping Fill, which changes the data in the DataSet
to match the data in the data source, and Update, which changes the data in the data
source to match the data in the DataSet. If you are connecting to a Microsoft SQL Server
database, you can increase overall performance by using the SqlDataAdapter along with
its associated SqlCommand and SqlConnection. For other OLE DB-supported databases,
use the DataAdapter with its associated OleDbCommand and OleDbConnection objects.

7.What happens when we issue Dataset.ReadXml command?

Reads XML schema and data into the DataSet.