ADO.NET Interview Questions

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What is Microsoft ADO.NET?
ADO.NET is one of the component in the Microsoft.NET framework which contains following features to Windows, web and distributed applications.

i. Data Access to the applications from Database in connected (Data reader object) and disconnected (Data set and data table) model.
ii. Modify the data in database from application.

What are the Benefits of ADO.Net?
ADO.Net offers following Benefits
Interoperability:
XML Format is one of the best formats for Interoperability.ADO.NET supports to transmit the data using XML format.

Scalability:
ADO.NET works on Dataset that can represent a whole database or even a data table as a disconnected object and thereby eliminates the problem of the constraints of number of databases being connected. In this way scalability is achieved.

Performance:
The performance in ADO.NET is higher in comparison to ADO that uses COM marshalling.

Programmability:
ADO.Net Data components in Visual studio help to do easy program to connect to the database.

Explain different connection objects used in ADO.NET?
Sqlconnection object used to connect to a Microsoft SQL Server database. SQL database connections use the SqlDataAdapter object to perform commands and return data.

OracleConnection object used to connect to Oracle databases. Oracle database connections use the OracleDataAdapter object to perform commands and return data. This connection object was introduced in Microsoft .NET Framework version 1.1.

OleDbConnection object used to connect to a Microsoft Access or third-party database, such as MySQL. OLE database connections use the OleDbDataAdapter object to perform commands and return data.

What are the different steps to access a database through ADO.NET?

• Create a connection to the database using a connection object.
• Open the Database Connection.
• Invoke a command to create a Dataset object using an adapter object.
• Use the Dataset object in code to display data or to change items in the database.
• Invoke a command to update the database from the Dataset object using an adapter object.
• Close the database connection.

What is the difference between Data Reader and Data Adapter?

• Data Reader is read only forward only and much faster than Data Adapter.
• If you use Data Reader you have to open and close connection explicitly where as if you use Data Adapter the connection is automatically opened and closed.
• Data Reader  expects connection to database to perform any operation on data where as Data Adapter is disconnected

What is the difference between Execute Reader, Execute Scalar and Execute Non Query methods?
Execute Reader
Execute Reader will be used to return the set of rows, on execution of SQL Query or Stored procedure using command object.

Execute Scalar
Execute Scalar will be used to return the single value, on execution of SQL Query or Stored procedure using command object.

Execute Non Query
If the command or stored procedure performs INSERT, DELETE or UPDATE operations, then we use Execute Non Query method. Execute Non Query method returns an integer specifying the number of rows inserted, deleted or updated.

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