ADO.NET Interview Questions and Answers
In this article, I am going to discuss frequently asked ADO.NET Interview Questions and Answers. If you face any questions in the interview that we are not covering here, please feel free to put that questions in the comment section, and definitely we will add that questions with answers.
What is ADO.NET?
ADO stands for Microsoft ActiveX Data Objects. ADO.NET is one of Microsoft’s Data Access Technologies using which we can communicate with different data sources. It is a part of the .NET Framework which is used to establish a connection between the .NET Application and different data sources. The Data Sources can be SQL Server, Oracle, MySQL, XML, etc. ADO.NET consists of a set of predefined classes that can be used to connect, retrieve, insert, update and delete data (i.e. performing CRUD operation) from data sources. ADO.NET mainly uses System.Data.dll and System.Xml.dll.
What are .NET Data Providers?
The Database cannot directly execute our C# code, it only understands SQL. So, if a .NET application needs to retrieve data or to do some insert, update, and delete operations from or to a database, then the .NET application needs to
- Connect to the Database
- Prepare an SQL Command
- Execute the Command
- Retrieve the results and display them in the application
And this is possible with the help of .NET Data Providers.
What are the objects of ADO.NET?
The Essential objects of ADO.Net are:
- Connection – SQLConnection, OracleConnection, OleDbConnection, OdbcConnection, etc.
- Command – SQLCommand, OracleCommand, OleDbCommand, OdbcCommand, etc.
- DataReader – SQLDataReader, OracleDataReader, OleDbDataReader, OdbcDataReader, etc.
- DataAdapter – SQLDataAdapter, OracleDataAdapter, OleDbDataAdapter, OdbcDataAdapter, etc.
- DataSet: The DataSet object is not specific to the provider-specific. Once you connect to a Database, execute the command, and retrieve data into the .NET application. The data can then be stored in a DataSet and work independently of the database. So, it is used to access data independently from any data sources. The DataSet contains a collection of one or more DataTable objects.
What does DataReader Object do?
The DataReader object of ADO.NET is used to provide access to data from a specified data source. It contains classes to sequentially read data from a data source like Oracle, MS Access, SQL Server, etc.
The ADO.NET SqlDataReader class in C# is used to read data from the SQL Server database in the most efficient manner. It reads data in the forward-only direction. It means, once it read a record, it will then read the next record, there is no way to go back and read the previous record.
The SqlDataReader is connection-oriented. It means it requires an open or active connection to the data source while reading the data. The data is available as long as the connection with the database exists
SqlDataReader is read-only. It means it is also not possible to change the data using SqlDataReader. You also need to open and close the connection explicitly.
Can we Load Multiple Tables in a Dataset?
Yes, you can load multiple tables in a dataset. Actually, a Dataset is a collection of data tables.
What are the Essential Features of ADO.NET?
- ADO.NET provides inbuilt classes to make a connection with databases like Oracle, SQL Server, MySQL, MS Access, etc.
- ADO.NET provides inbuilt classes for data manipulation operations like Insert, Update, Delete and Select data.
- Provide a function to combine data from different data sources.
- Disconnect data architecture for better performance.
What are the advantages of ADO.NET?
The following are the advantages of ADO.NET:
What are the main differences between classic ADO and ADO.NET?
These are the main differences between ADO and ADO.NET:
- ADO has a record set.
- The objects of ado communicate in binary mode.
- It supports mostly connection-oriented models.
- It derives information about data implicitly at runtime based on metadata, so it is a costly process.
- It allows only client-side cursors.
- ADO.NET have a data adopter and data set.
- It uses XML for passing the data.
- It works in disconnected manners.
- It uses known metadata at design time, so it provides better runtime performance and more consistent runtime behavior.
- It supports both client-side and server-side cursors.
Which ADO.NET object is very fast in getting data from the database?
What is connection pooling?
Connection pooling means, once the connection object is open, rather than going and recreating the connection object again and again, ADO.NET does, is it takes the connection object and puts it into a place called pooler. In the pooler, the object will be cached, and later if somebody says connection.open then rather than executing the series of steps, it takes the connection object from the pool and start executing.
What are the ADO.NET Connection Pooling Parameters?
- Connection Lifetime: default value is 0.
- Connection Timeout: default value is 15.
- Max Pool Size: default value is 100.
- Min Pool Size: default value is 0.
- Pooling: default values are true.
- Increment Pool Size: default value is 5.
- Decrement Pool Size: default value is 1.
Can we use the stored procedure in ADO.NET?
Yes, we can use a stored procedure in ADO.NET. It makes the performance fast because stored procedures are precompiled.
What is the use of Dataview?
Dataview is used to represent a whole table or a part of the table. It is used for sorting and searching data in the data table.
What is the difference between Data Reader and Data Adapter?
- The Data reader is read-only, forward only. It is much faster than a data adopter.
- Data reader facilitates you to open and close connections explicitly.
- The data reader makes a connection to the database to operate on data.
- It is comparatively slower.
- If you use a data adopter, the connection is automatically open and closed.
- The data adopter is disconnected.
What is the usage of the DataSet object in ADO.NET?
The DataSet represents a subset of the database in memory. That means the ADO.NET DataSet is a collection of data tables that contains the relational data in memory in tabular format.
It does not require a continuous open or active connection to the database. The DataSet is based on the disconnected architecture. This is the reason why it is used to fetch the data without interacting with any data source. We will discuss the disconnected architecture of the data set in our upcoming articles.
What are the different ADO.NET Namespaces?
A list of ADO.NET Namespaces:
- System.Data: It contains the definition for columns, relations, tables, databases, rows, views, and constraints.
- System.Data.SqlClient: It contains the classes that are used to connect to a Microsoft SQL Server database such as SqlCommand, SqlConnection, and SqlDataAdapter.
- System.Data.Odbc: It contains classes required to connect to most Odbc Drivers. These classes include OdbcCommand, OdbcConnection.
- System.Data.OracleClient: It contains classes such as OracleConnection, and OracleCommand required to connect to an Oracle database.
Why is Stored Procedure used in ADO.NET?
The stored Procedure is used for the following reasons:
- To improve performance
- Easy to use and maintain
- For security
- Less time is taken for execution
- Less Network Traffic
What is the difference between Data Grid and Data Repeater?
- Data grid has advanced features and facilitates you to do many things like paging and sorting your data without much effort.
- Data grid can hold text data, but not linked or embedded objects.
- A data repeater doesn’t have the paging feature, but it can be done by coding.
- A data repeater can hold other controls and can embed objects.
- A data repeater can embed a data grid within it but vice versa is not possible.
What is the difference between DataReader and DataSet?
A list of differences between DataReader and DataSet:
- Forward only.
- Connected recordset.
- Single table involved.
- No relationship is required.
- No XML storage.
- Occupies less memory.
- Loop through the DataSet.
- Disconnected recordset.
- Multiple tables are involved.
- A Relationship between tables is maintained.
- Can be stored as XML.
- Occupies more memory.
- Can do addition /Updation and deletion
What is a Linked Server?
A linked server is used to enable the SQL server to execute commands against OLE DB data sources on remote servers.
What is the default timeout specified for the “SqlCommand.CommandTimeout” property?
The default timeout for SqlCommand.CommandTimeout property is 30 seconds.
What are the several execution methods of ADO.NET?
These are the different execution methods of the ADO.NET command object:
- ExecuteScalar: It returns a single value from the dataset.
- ExecutenonQuery: It has multiple values and returns resultset from the dataset.
- ExecuteReader: Forward-only Resultset.
- ExecuteXMLReader: Build XMLReader object from the SQL Query.
What are the important features of ADO.NET 2.0?
Most important features of ADO.NET 2.0:
- Bulk Copy Operation: It facilitates bulk copy operation from one Data Source to another Data Source.
- Batch Update: To update n no of rows in a database table in a single call from a program thus avoiding a round trip to the database.
- Data Paging: To read data from a certain index
- Connection Details: To get detailed info about connections like buffer information, cursor details, etc.
- DataSet.RemotingFormat Property: To make the dataset serialized in Binary
- DataTable’s Load and Save Methods: For XML interactions.
In this article, I am providing the list of Frequently Asked ADO.NET Interview Questions and Answers. I hope you enjoy this ADO.NET Interview Questions and Answers article. If you want to share any questions and answers, please put the same in the comment section which will benefit others.
About the Author: Pranaya Rout
Pranaya Rout has published more than 3,000 articles in his 11-year career. Pranaya Rout has very good experience with Microsoft Technologies, Including C#, VB, ASP.NET MVC, ASP.NET Web API, EF, EF Core, ADO.NET, LINQ, SQL Server, MYSQL, Oracle, ASP.NET Core, Cloud Computing, Microservices, Design Patterns and still learning new technologies.