Top 50 ADO.NET Interview Questions and Answers for 2024

Advantages of ADO.NET

ADO.NET has multiple advantages. Let us go through a few of them:

• Interoperability: Communication across heterogeneous environments is possible with ADO.NET.
• Scalability: ADO.NET can manage a large number of clients without burdening the performance of the system. Thus, ADO.NET is highly scalable as it can be easily expanded as and when required.
• Productivity: It supports the development of robust applications for data access using rich and extensible component object models.
• Performance: ADO.NET can establish connections quickly to fetch data without any delay.

Scope of ADO.NET

ADO.NET as a product of Microsoft has an excellent standing in the market along with massive community support. You can learn ADO.NET along with hands-on experience on the .NET framework, which will give you a competitive advantage. 

Top ADO.NET Interview Questions and Answers

ADO.NET being one of the most in-demand subjects, we have collated a list of the top 50 ADO.NET interview questions along with answers for freshers striving for a career in the programming field. Do go through the following questions to gain a better understanding of ADO.NET.

1. What is ADO.NET?

ADO.NET is the abbreviation for ActiveX Data Object. It is a part of the .NET Framework by Microsoft that provides a set of classes that can be used to handle data interaction with data sources such as databases (for example, Oracle, SQL, MySQL, MS Access, and so on.) and XML files. ADO.NET has the ability to separate mechanisms for data access, data connectivity, and data manipulation. Another feature of ADO.NET is that it has introduced the disconnected architecture, in which data can be stored in a DataSet. The ADO.NET classes are stored in the DLL called System.Data.dll.

2. What are the objects of ADO.NET?

The two main objects of ADO.Net are:

• DataSet
• DataReader

3. Explain the two main objects of ADO.NET

• The DataReader object of ADO.NET helps with the access of data from a particular data source. It comprises classes to read data sequentially from a data source such as MS Access, Oracle, SQL Server, and so on.
• The DataSet object of ADO.NET is key to supporting distributed, disconnected data scenarios with ADO.NET. The DataSet is a memory-resident depiction of data that offers a reliable relational programming model irrespective of the data source.

4. What are the main differences between ADO.NET and the classic ADO?

Following are the main differences between ADO and ADO.NET:

5. Explain the term LINQ with respect to ADO.NET?

LINQ stands for Language-Integrated Query. It is a native query language for the .NET framework. It is exclusively designed to manage queries with .NET applications and can be connected with MS Access and SQL.

6. Explain the difference between ADO.NET and ASP.NET.

The main differences between ADO.NET and ASP.NET are:

7. Explain about DataSet types in ADO.NET.

DataSet is a set of database tables (column and row format) that comprises the data. The two types of DataSet in ADO.NET are:

• Typed DataSet: A typed DataSet is a result from the DataSet base class and can be created by choosing the DataSet option in Visual Studio. It is created as an XML schema (.xsd file) that comprises DataSet structure information such as tables, columns, and rows. Data from the database is transferred into a dataset and from there to another component in the XML format.
• Untyped DataSet: Untyped DataSet does not have any associated XML schemas. Users are supposed to add tables, columns, and other elements to it. Properties can be set during design time or run time.

8. What is connection pooling?

Connection pooling comprises database collections. This helps with the usage or reuse of that connection whenever there is a request to the database. This technique helps with the performance efficiency of executing the database commands as a new connection need not be created.

9. Explain the ADO.NET connection pooling parameters?

• Connection Timeout: default value is set to 15.
• Connection Lifetime: default value is set to 0.
• Min Pool Size: default value is set to 0.
• Max Pool Size: default value is set to 100.
• Incr Pool Size: default value is set to 5.
• Decr Pool Size: default value is set to 1.
• Pooling: default values are true.

10. What is the use of Dataview?

Dataview represents a whole table or a part of the table. It is used for searching and sorting data in the data table.

11. Name the data providers in ADO.NET?

Following are the data providers in ADO.NET:

• OLEDB
• MS SQL Server
• ODBC

12. How is the DataSet object used in ADO.NET?

DataSet object is a main component of ADO.NET as it reduces the load on the database.

13. Provides some information on the ADO.NET namespaces:

Following are the different namespaces in ADO.NET:

• System.Data: Comprises the definition for relations, columns, database, tables, rows, constraints, and views.
• System.Data.SqlClient: Comprises the classes used to link to a Microsoft SQL Server database such as SqlCommand, SqlConnection, SqlDataAdapter.
• System.Data.Odbc: Comprises classes required to connect to most ODBC Drivers.
• System.Data.OracleClient: Contains classes such as OracleConnection and OracleCommand to connect to an Oracle database.

14. Which are the different layers of ADO.NET?

The different layers of ADO.NET are:

• Business Logic Layer
• Presentation Layer
• Database Access Layer

15. Why is the Stored Procedure used in ADO.NET?

Stored Procedure is used for the following reasons:

• To enhance performance
• For security
• Less time for execution
• Easy to maintain and use
• Less Network Traffic

16. What is a linked server?

A linked server enables the SQL server to implement commands against OLE DB data sources on remote servers.

17. What is the default timeout stated for the "SqlCommand.CommandTimeout" property?

The default timeout for SqlCommand.CommandTimeout property is 30 seconds.

18. What are the several execution methods of ADO.NET?

Following are the execute methods of a ADO.NET command object:

• ExecutenonQuery: Has various values and returns resultset from the dataset.
• ExecuteScalar: Returns a single value from the dataset.
• ExecuteXMLReader: Build XMLReader object from the SQL Query.
• ExecuteReader: Forward-only Resultset.

19. What is object pooling?

Object pooling is a storehouse of the objects in memory that can be used later. Object pooling reduces the load of the object creation when required. 

20. What is Data view?

Data view is the depiction of data in various formats and it can be requested by the users. Data can be exposed in different filters or sort orders on the user condition with the help of Data view.

21. What is the use of a connection object?

ADO.Net Connection object establishes a connection between the data source and application.

22. What are all features of ADO.Net?

Following are the features of ADO.Net:

• Data Paging
• New Data Controls
• Bulk Copy Operation
• Datareader’s execute methods

23. What is the difference between Reponse.ExpiresAbsolute and Response.Expires?

The Response.ExpiresAbsolute property gives an exact time at which the page in cache expires. Whereas Response.expires property specifies the minutes of the page in cache from the time the request has been sent from server.

24. What is boxing and unboxing?

Change of value type to reference type is Boxing and change of reference to value type is unboxing. Boxing and unboxing are used for type casting.

25. Is it possible to edit data in Repeater control?

No, it is not possible to modify data in the Repeater control.

26. What are the differences between OLEDB and SQLClient Providers?

The OLEDB provider helps access any database and offers flexibility of modifying the database at any time. SQLClient provider helps to access only the SQL Server database.

27. What are all the commands used with Data Adapter?

DataAdapter retrieves data from a data source. UpdateCommand, Insertcommand, and DeleteCommand are the commands object used in DataAdapter to handle a modification on the database.

28. What is the difference between Dataset.clone and Dataset.copy?

• Dataset.clone object copies structure of the dataset, including relations, schemas, and constraints. This does not copy data in the table.
• Dataset.copy – Copies both data and structure from the table.

29. What is the difference between Command and CommandBuilder objects?

Command executes all kinds of queries such as DML and DDL. DML are the Insert, Update and Delete commands. DDL is like Create and Drop tables.

Command Builder object is used to create and execute DDL queries such as Create and Drop Tables.

30. Is it possible to load multiple tables in a Dataset?

Yes, we can load different tables in a single dataset.

31. Which provider is used to connect MS Access, Oracle, and so on?

ODBC and OLEDB Providers are used to establish links to Oracle and MS Access. Oracle Data Provider is also used to establish a link with the oracle database.

32. Can stored procedures be used in ADO.Net?

Yes, stored procedures can be used ADO.Net and these procedures can also be used for common repetitive functions.

33. What are the methods of an XML dataset object?

There are different methods of an XML dataset object:

• WriteXml() – Copies the contents of Dataset to a file.
• WriteXmlSchema() – Copies XSD Schema into a file.
• GetXml() – Receives the XML data in a Dataset as a single string.
• GetXmlSchema() – Receives XSD Schema in a Dataset as a single string.
• ReadXml() – Reads XML data from a file.
• ReadXmlSchema() – Reads XML schema from a file.

34. What are all the different authentication techniques used to connect to MS SQL Server?

An SQL Server should authenticate before performing any activity in the database. There are two kinds of authentication:

• Windows and SQL Server Authentication Mode – Authentication with the combination of both SQL Server and Windows Authentication.
• Windows Authentication – Authentication using only the Windows domain accounts.

35. Name the method that the command class uses to execute SQL statements that return a single value?

The command class uses the Execute Scalar method to execute SQL statements that can return single values.

36. Which keyword is used to accept a variable number of parameters?

The Params keyword is used to accept the variable number of parameters.

37. Which method of the XML object is used to read an XML file on a daily basis?

The ReadXML() method is used to read XML files.

38. Which method in OLEDBAdapter is used to add records in a dataset?

The Fill Method is used to populate records in a dataset.

39. Name the object that needs to be closed in ADO.NET?

The OLEDBConnection and OLEDBReader objects need to be closed in ADO.NET. These objects remain in the memory not closed properly.

40. How to stop thread running?

Use the Thread.Abort() function to stop the thread execution at any time.

41. Which method is used to sort the data in ADO.Net?

The Sort() method of GridViewControl sorts the data in a data table.

42. Which object is used to add a relationship between two Data tables?

The DataRelation object adds a relationship between two or more data table objects.

43. Which is the best method to be able to access two values within the database?

ExecuteNonQuery is the best method to gain access to two values within the database.

44. What are all the classes that are available in System.Data Namespace?

Following are the classes that are available in System.Data Namespace:

• DataTable
• Dataset.
• DataRow.
• DataColumn.
• DataRelation.
• Constraint.

45. What are the classes in System.Data.Common Namespace?

The following two classes are involved in System.Data.Common Namespace:

• DataColumnMapping.
• DataTableMapping.

46. What do you understand about the ExecuteNonQuery Method?

The ExecuteNonQuery method executes the command and returns the number of rows affected.

47. What do you understand from the DataRelation class?

The DataRelation is a class of disconnected architecture in the .NET framework. It is found in the System.Data namespace.

48. How to Connect to a Database using ADO.NET:

One must be familiar with connection strings to create a connection. A connection string is needed as a parameter to an SQLConnection. A ConnectionString is a string variable (not case sensitive). This contains value and key pairs, such as server, database, provider, userid and word as in the following:

• Server="nameof the server or IP Address of the server"
• Database="name of the database"
• userid="user name who has permission to work with database"
• word="the word of userid"

49. What is the HasChanges() method of DataSet?

The HasChanges() method returns a boolean value to show whether the record of DataSet has been modified or not. It returns true if any modifications are made and false if no modifications have been made.

50. What is connected and disconnected data in ADO.NET?

The connected environment offers forward-only, read-only access to data in the data source and the capability to implement commands against the data source. The disconnected environment allows for the manipulation of data that has been retrieved from the data source that can be reconciled with the data source later.

Conclusion

This article has provided you with the most commonly asked ADO.NET interview questions that can help you get a job in the programming field. Make sure you go through all the questions and answers provided in this blog. 

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