ADO.NET Interview Questions for Junior (Answers & Examples)

Did you know that ADO.NET remains one of the most essential technologies for database access in .NET applications? Many junior developers struggle with database connectivity, query execution, and data manipulation during interviews. But don’t worry! If you’re preparing for an interview, mastering ADO.NET concepts is essential. Interviewers often test your understanding of how ADO.NET connects with databases and manages data. This post covers the top 10 ADO.NET interview questions along with detailed answers and code examples to help you ace your interview.

1. What is ADO.NET? How does it work?

Answer:

ADO.NET (ActiveX Data Objects for .NET) is a data access technology in .NET used to interact with databases such as SQL Server, MySQL, and Oracle. It provides a bridge between an application and a database by using connections, commands, readers, and datasets.

Example:

using System;
using System.Data;
using System.Data.SqlClient;

class Program {
    static void Main() {
        string connString = "{your_connection_string}";
        using (SqlConnection conn = new SqlConnection(connString)) {
            conn.Open();
            Console.WriteLine("The connection is established successfully.");
        }
    }
}

2. What are the basic components of ADO.NET?

Answer:

The primary components of ADO.NET are:

• Connection: Establishes a connection to the database (e.g., SqlConnection).
• Command: Executes SQL commands (SqlCommand).
• DataReader: Reads data in a forth-only, read-only manner (SqlDataReader).
• DataAdapter: Bridges DataSet and the database.
• DataSet: Stores disconnected data.

3. What is the difference between DataSet and DataReader?

Example:

SqlDataReader dataReader = command.ExecuteReader(); // Connected
DataSet dataSet = new DataSet(); // Disconnected

4. How to execute SQL query with ADO.NET?

Answer:

You can execute a query using SqlCommand with ExecuteNonQuery for non-select queries or ExecuteReader for retrieving data.

Example:

using (var connection = new SqlConnection(connectionString)) {
    connection.Open();
    string query = "INSERT INTO Users (Name, Age) VALUES ('John Doe', 30)";
    SqlCommand command = new SqlCommand(query, connection);
    int rowsAffected = command.ExecuteNonQuery();
    Console.WriteLine($"Users Inserted: {rowsAffected}");
}

5. What’s the purpose of SqlDataAdapter?

Answer:

SqlDataAdapter is used to fill a DataSet with data from the database and update the database based on changes made to the DataSet.

Example:

SqlDataAdapter dataAdapter = new SqlDataAdapter("SELECT * FROM Users", connection);
DataSet dataSet = new DataSet();
dataAdapter.Fill(dataSet);

6. How to handle database transactions in ADO.NET?

Answer:

You can use SqlTransaction to ensure atomicity and consistency of database operations.

Example:

using (var connection = new SqlConnection(connectionString)) {
    connection.Open();
    SqlTransaction transaction = connection.BeginTransaction();
    try {
        SqlCommand command = new SqlCommand("UPDATE Employees SET Age = Age + 1", connection, transaction);
        command.ExecuteNonQuery();
        transaction.Commit();
    } catch {
        transaction.Rollback();
    }
}

7. What is the different between Execute methods in ADO.NET?

Answer:

8. How to use connection pooling in ADO.NET?

Answer:

Connection pooling improves performance by reusing database connections. ADO.NET automatically manages it using connection strings.

Example:

string connString = "Data Source=server;Initial Catalog=database;Integrated Security=True;Pooling=true;";

9. What is the difference between ADO.NET and Entity Framework?

10. What are common performance optimization techniques in ADO.NET?

Answer:

• Use connection pooling.
• Use parameterized queries to prevent SQL injection.
• Use batch processing instead of multiple queries.
• Use DataReader instead of DataSet when possible.

Example of Parameterized Query:

string query = "INSERT INTO Users (Name, Age) VALUES (@name, @age)";
SqlCommand command = new SqlCommand(query, connection);
command.Parameters.AddWithValue("@name", "Alice");
command.Parameters.AddWithValue("@age", 28);
command.ExecuteNonQuery();

Conclusion: Master ADO.NET for Your Interview Success

These top 10 ADO.NET interview questions will help you solidify your understanding of ADO.NET fundamentals. Understanding these concepts will not only boost your confidence but also impress your interviewer.

What question did you find the most challenging? Let us know in the comments!

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