Q. 1 What
are major difference between classic ADO and ADO.NET ?
A. Following are
some major differences between both Ado and Ado.Net
? As in classic ADO we had client and server side cursors
they are no more present in ADO.NET. Note it's a disconnected model so they are
no more applicable.
? Locking is not supported due to disconnected model.
? All data persist in XML as compared to classic ADO where
data persisted in Binary format also.
Q.2 What
is ADO.NET?
A. ADO.Net is the part of the Microsoft .Net Framwork. This framwork provides the set of
classes that deals with a data
communication between various layers of the Software Architecture and the
database.
Q.3 DataAdapter
Object populates a DataSet and resolves updates with the DataSource. Yes/no?
A. yes.
Q.4 What is the role of data provider?
A. The .NET data
provider layer resides between the application and the database. Its task is to
take care of all their interactions.
The .NET Data provider can be demonstrated to be:
SQL Server data provider
OLEDB data provider
ODBC Data Provider
ADO.NET supports the following OLE DB Providers:
-SQLOLEDB - Microsoft OLE DB Provider for SQL Server.
- MSDAORA - Microsoft OLE DB Provider for Oracle.
- Microsoft.Jet.OLEDB.4.0 - OLE DB Provider for Microsoft
Jet.
Q 5. How does object pooling and connection pooling
differ?
A. In Object pooling,
you can control the number of connections.
In connection pooling, you can control the maximum number
reached.
When using connection pooling, if there is nothing in the
pool, a connection is created since the creation is on the same thread.
In object pooling, the pool decides the creation of an object
depending on whether the maximum is reached which in case if it is, the next
available object is returned. However, this could increase the time complexity
if the object is heavy.
Q.6 what is the NameSpace in which .Net has the
data functionality classes?
A. Following are the NameSpaces provided by .NET for data
management :-
system.Data;
system.data.oledb;
system.data.sqlclient;
system.xml; etc....
Q.7 Can you give an overview of ADO .NET
architecture?
A. The most important
section in ADO.NET architecture is “Data Provider”. Data Provider provides
access to datasource (SQL SERVER, ACCESS, ORACLE).In short it provides object
to achieve functionalities like opening and closing connection, retrieve data
and update data. In the below figure you can see the four main sections of a
data provider :-
? Connection.
? Command object (This is the responsible object to use
stored procedures) .
? Data Adapter (This object acts as a bridge between
datastore and dataset).
? Datareader (This object reads data from data store in
forward only mode).
Q.8 What are the two fundamental objects in
ADO.NET ?
A. Datareader and
Dataset are the two fundamental objects in ADO.NET.
Q.9 What is difference between dataset and datareader
?
A. Following are
some major differences between dataset and datareader :-
? DataReader provides forward-only and read-only access to
data, while the DataSet object can hold more than one table (in other words
more than one rowset) from the same data source as well as the relationships
between them.
? Dataset is a disconnected architecture while datareader is
connected architecture.
? Dataset can persist contents while datareader can not
persist contents, they are forward only.
Q.10 What is the use of command objects and what
are the methods provided by the command object ?
A. They are used to connect connection object to Datareader
or dataset.
Following are the methods provided by command object :-
ExecuteScaller();
ExecuteNonquery();
ExecuteReader();
Q.11 How can
we force the connection object to close after my datareader is closed ?
A. Command method Executereader takes a parameter called as
CommandBehavior where in we can specify
saying close connection automatically after the Datareader is close.
pobjDataReader =
pobjCommand.ExecuteReader(CommandBehavior.CloseConnection)
Q.12 I want
to force the datareader to return only schema of the datastore rather than data
?
A. pobjDataReader = pobjCommand.ExecuteReader(CommandBehavior.SchemaOnly)
Q.13 How
can we fine tune the command object when we are expecting a single row or a
single value ?
A. Again CommandBehaviour enumeration provides two values
SingleResult and SingleRow. If you are expecting a single value then pass
“CommandBehaviour.SingleResult” and the query is optimized accordingly, if you
are expecting single row then pass “CommandBehaviour.SingleRow” and query is
optimized according to single row.
Q.14 Which
is the best place to store connectionstring in .NET project?
A.Config files are the best places to store
connectionstrings.
If it is a web-based
application “Web.config” file will be used and if it is a windows application
“App.config” files will be used.
Q.15 What is
the use of dataadapter?
A.These are objects that connect one or more Command objects
to a Dataset object. They provide logic that would get data from the data store
and populates the tables in the DataSet, or pushes the changes in the DataSet
back into the data store.
An OleDbDataAdapter
object is used with an OLE-DB provider.
A SqlDataAdapter
object uses Tabular Data Services with MS SQL Server.
There are three most commonly used methods of Dataadapter :-
Fill();
updata();
FillSchema();
Q.16 How can we save all data from dataset ?
A.Dataset has “AcceptChanges” method which commits all the
changes since last time “Acceptchanges” has been executed.
Q.17 How can we add/remove row’s in “DataTable”
object of “DataSet” ?
A.“Datatable” provides “NewRow” method to add new row to
“DataTable”.
“DataTable” has “DataRowCollection” object which has all
rows in a “DataTable” object.
Following are the methods provided by “DataRowCollection”
object :-
add();
remove();
removeat();
Q.18 What is basic use of “DataView” ?
A.“DataView” represents a complete table or can be small
section of rows depending on some criteria. It is best used for sorting and
finding data with in “datatable”. Dataview has the following method’s :-
Find();
Findrow();
addnew();
delete();
Q.19 What
is the use of CommandBuilder ?
A.CommandBuilder builds “Parameter” objects automatically.
Below is a simple code which uses commandbuilder to load its parameter objects.
Dim
pobjCommandBuilder As New OleDbCommandBuilder(pobjDataAdapter)
pobjCommandBuilder.DeriveParameters(pobjCommand)
Be careful while using “DeriveParameters” method as it needs
an extra trip to the Datastore which can be very inefficient.
Q.20 What’s difference between “Optimistic”
and “Pessimistic” locking?
A. In pessimistic
locking when user wants to update data it locks the record and till then no one
can update data. Other user’s can only view the data when there is pessimistic
locking.
In optimistic
locking multiple users can open the same record for updating, thus increase
maximum concurrency. Record is only locked when updating the record. This is
the most 299 preferred way of locking practically. Now a days browser based
application is very common and having pessimistic locking is not a practical
solution.
Q.21 How
many ways are there to implement locking in ADO.NET ?
A. Following are the ways to implement locking using ADO.NET
:-
1) When we call “Update” method of DataAdapter it handles
locking internally .
2) Define a Datetime stamp field in the table.When actually
you are firing the UPDATE SQL statements compare the current timestamp with one
existing in the database.
3) Define a Datetime stamp field in the table.When actually
you are firing the UPDATE SQL statements compare the current timestamp with one
existing in the database.
Q.22 What is difference between Dataset. clone and
Dataset. copy ?
A. Clone: - It only
copies structure, does not copy data. Copy: - Copies both structure and data.
Q.23 Can you explain the difference between an
ADO.NET Dataset and an ADO Recordset?
A. There two main basic differences between recordset and
dataset :-
1) With dataset you can retrieve data from two databases
like oracle and sql server and merge them in one dataset , with recordset this
is not possible.
2) All representation
of Dataset is using XML while recordset uses COM.
3) Recordset can not
be transmitted on HTTP while Dataset can be
.
Q. 24 What is Maximum Pool Size in ADO.NET
Connection String?
A. Maximum pool
size decides the maximum number of connection objects to be pooled. If the
maximum pool size is reached and
there is no usable connection available the request is queued until connections
are released back in to pool. So it’s always a good habit to either call the
close or dispose method of the connection as soon as you have finished work
with the connection object.
Q.25 How to enable and disable connection pooling?
A. For .NET it is
enabled by default but if you want to just make sure set Pooling=true in the
connection string. To disable connection pooling set Pooling=false in
connection string if it is an ADO.NET Connection. If it is an OLEDBConnection
object set OLE DB Services=-4 in the connection string.
Q.26 Explain
the three services model?
A.Three-tier application:-
1) .
Presentation (UI),
2) business (logic and underlying code) and
3) data (from
storage or other sources).
Q. 27 What
does the parameter Initial Catalog define inside Connection String?
A.The database name to connect to.
Q.28 What's the data provider name to connect to
Access database?
A. Microsoft.Access.
Q.29 What
does Dispose method do with the connection object?
A.Deletes it from the memory.
Q. 30 What
is a pre-requisite for connection pooling?
A. Multiple processes
must agree that they will share the same connection, where every parameter is
the same, including the security settings.
Q.31 which
of the following is the method provided by the DataSet Object to generate XML?
A. ReadXML,WritenXML
and GetXML.
Q.32 when
you create a relation between tables in ADO.Net
DataSet?
A. 1) a UniqueConstraint is added to the parent table ,
2) a ForeignKeyConstraint is added to the child
table by default .
Q.33How to
run a stored procedure from .Net code?
A. use the command object and it's ExecuteNonQuery method to
run a DDL or DDL statements of SQL.
First we create connection object an command object and configure these objects
for the statement you wish to exicute . Open the database connection.call
ExecuteNonQuery on the command. Close
the connection.
Q.34 what is
the SelectCommandBuilder in ADO. Net?
A. SelectCommandBuilder is class in
ADO.Net provides the feature of reflecting the changes made to a dataset
or an instance of the sql server data. The scb object
automatically genarates the values contained with in the sqldataadapter's
Insertcommand, updatecommand and deletecommand properties based on the initial selectcommand. The advantage is here
is that will not need to write
selectcommand and sqlparameter
stype explicitly.
Q.35 which
method of the command object is best suited
when you have aggregate functions in a select statements?
A. ExecuteScalar.
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Q.36.
|
How
do I delete a row from a DataTable?
|
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ds.Tables("data_table_name").Rows(i).Delete
dscmd.update(ds,"data_table_name") |
Q.37. What
is diffgram?
a.It is a format which dataset use internally while come with
xml files.
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