1) What is the namespace
in which .NET has the data functionality class?
Following are the namespaces provided by
.NET for data management:-
System. Data
This contains the basic objects used for accessing and storing relational data, such as DataSet, DataTable, and Data Relation. Each of these is independent of the type of data source and the way we connect to it.
This contains the basic objects used for accessing and storing relational data, such as DataSet, DataTable, and Data Relation. Each of these is independent of the type of data source and the way we connect to it.
System.Data.OleDB
It contains the objects that we use to connect to a data source via an OLE-DB provider, such as OleDbConnection, OleDbCommand, etc. These objects inherit from the common base classes, and so have the same properties, methods, and events as the SqlClient equivalents.
It contains the objects that we use to connect to a data source via an OLE-DB provider, such as OleDbConnection, OleDbCommand, etc. These objects inherit from the common base classes, and so have the same properties, methods, and events as the SqlClient equivalents.
System.Data.SqlClient:
This contains the objects that we use to connect to a data source via the Tabular Data Stream (TDS) interface of Microsoft SQL Server (only). This can generally provide better performance as it removes some of the intermediate layers required by an OLE-DB connection.
This contains the objects that we use to connect to a data source via the Tabular Data Stream (TDS) interface of Microsoft SQL Server (only). This can generally provide better performance as it removes some of the intermediate layers required by an OLE-DB connection.
System.XML
This Contains the basic objects required to create, read, store, write, and manipulate XML documents according to W3C recommendations.
This Contains the basic objects required to create, read, store, write, and manipulate XML documents according to W3C recommendations.
2) Can you give an overview of
ADO.NET architecture?
The most important section in ADO.NET architecture is “Data Provider”. Data Provider provides access to data source (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:-
Figure: - ADO.NET Architecture
• Connection
• Command object (This is the responsible object to use stored procedures)
• Data Adapter (This object acts as a bridge between data store and dataset)
• Data reader (This object reads data from data store in forward only mode).
• Dataset object represents disconnected and cached data. If you see the diagram, it is not in direct connection with the data store (SQL SERVER, ORACLE etc) rather it talks with Data adapter, who is responsible for filling the dataset. Dataset can have one or more Data table and relations
• Data View” object is used to sort and filter data in Data table.
Note:- This is one of the favorite questions in .NET. Just paste the picture in your mind and during interview try to refer that image.
• Command object (This is the responsible object to use stored procedures)
• Data Adapter (This object acts as a bridge between data store and dataset)
• Data reader (This object reads data from data store in forward only mode).
• Dataset object represents disconnected and cached data. If you see the diagram, it is not in direct connection with the data store (SQL SERVER, ORACLE etc) rather it talks with Data adapter, who is responsible for filling the dataset. Dataset can have one or more Data table and relations
• Data View” object is used to sort and filter data in Data table.
Note:- This is one of the favorite questions in .NET. Just paste the picture in your mind and during interview try to refer that image.
3) What are the two fundamental
objects in ADO.NET?
Data reader and Dataset are the two fundamental objects in ADO.NET.
4) What is difference between dataset and data reader?
Following are some major differences between dataset and data reader:-
• Data Reader 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 row set) from the same data source as well as the relationships between them.
• Dataset is a disconnected architecture while data reader is connected architecture.
• Dataset can persist contents while data reader cannot persist contents, they are forward only.
5) What are major difference between classic ADO and ADO.NET?
Following are some major differences between both :-
• In ADO we have recordset and in ADO.NET we have dataset.• In recordset we can only have one table. If we want to accommodate more than one tables we need to do inner join and fill the recordset. Dataset can have multiple tables.
• All data persist in XML as compared to classic ADO where data persisted in Binary format also.
6) What is the use of connection
object?
They are used to connect a data to a Command object.
• An OleDbConnection object is used with an OLE-DB provider
• A SqlConnection object uses Tabular Data Services (TDS) with MS SQL Server
7) What is the use of command
objects?
They are used to connect connection object to Data reader or dataset. Following are the methods provided by command object:-
• ExecuteNonQuery: -
Executes the command defined in the Command
Text property against the connection defined in the Connection property for a
query that does not return any row (an UPDATE, DELETE, or INSERT). Returns an
Integer indicating the number of rows affected by the query.
• ExecuteReader: -
Executes the command defined in the Command
Text property against the connection defined in the Connection property.
Returns a "reader" object that is connected to the resulting row set
within the database, allowing the rows to be retrieved.
• ExecuteScalar: -
Executes the command defined in the Command
Text property against the connection defined in the Connection property.
Returns only single value (effectively the first column of the first row of the
resulting row set any other returned columns and rows are discarded. It is fast
and efficient when only a "singleton" value is required
8)What is the use of data
adapter?
These objects 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.
9)What are basic methods of Data
adapter?
There are three most commonly used methods of Data adapter:-
Fill: -
Executes the Select Command to fill the
Dataset object with data from the data source. It an also be used to update
(refresh) an existing table in a Dataset with changes made to the data in the
original data source if there is a primary key in the table in the Dataset.
FillSchema :-
Uses the SelectCommand to extract just the
schema for a table from the data source, and creates an empty table in the
DataSet object with all the corresponding constraints.Update:- Calls the
respective InsertCommand, UpdateCommand, or DeleteCommand for each inserted, updated,or deleted
row in the DataSet so as to update the original data source with the changes
made to the content of the DataSet. This is a little like the UpdateBatch
method provided by the ADO Recordset object, but in the DataSet it can be used
to update more than one table.
10) What is Dataset object?
The Dataset provides the basis for disconnected storage and manipulation of relational data. We fill it from a data store, work with it while disconnected from that data store, then reconnect and flush changes back to the data store if required.
11) What are the various objects
in Dataset?
Dataset has a collection of Data Table object within the Tables collection. Each Data Table object contains a collection of Data Row objects and a collection of Data Column objects. There are also collections for the primary keys, constraints, and default values used in this table, which is called as constraint collection, and the parent and child relationships between the tables. Finally, there is a Default View object for each table. This is used to create a Data View object based on the table, so that the data can be searched, filtered, or otherwise manipulated while displaying the data.
Note: - Look back again to the main diagram
for ADO.NET architecture for visualizing this answer in pictorial form.
