Interview Q&A

Short answer: mount of data quickly and do not need to modify the data.

Explain a bit more

It requires an open connection to the database and reads data sequentially, one row at a time. mount of data quickly and do not need to modify the data. It requires an open connection to the database and reads data sequentially, one row at a time. mount of data quickly and do not need to modify the data. It requires an open connection to the database and reads data sequentially, one row at a time. SqlCommand command = new SqlCommand("SELECT CustomerName FROM Customers", connection); SqlDataReader reader = command.ExecuteReader(); while (reader.Read()) { Console.WriteLine(reader["CustomerName"]); } reader.Close(); mount of data quickly and do not need to modify the data. It requires an open connection to the database and reads data sequentially, one row at a time.

Example code

SqlCommand command = new SqlCommand("SELECT CustomerName FROM Customers", connection); SqlDataReader reader = command.ExecuteReader(); while (reader.Read()) { Console.WriteLine(reader["CustomerName"]); } reader.Close();

Real-world example (ShopNest)

For large order exports, ShopNest uses SqlDataReader (forward-only, fast). DataSet is heavier and mainly for disconnected editing scenarios.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: The SqlDataReader is used to retrieve data from the database in a forward-only and read-only manner. It is more efficient than a DataSet when you need to retrieve a large amount of data quickly and do not need to modify the data. It requires an open connection to the database and reads data sequentially, one row at a time.

Example code

SqlCommand command = new SqlCommand("SELECT CustomerName FROM Customers", connection); SqlDataReader reader = command.ExecuteReader(); while (reader.Read()) { Console.WriteLine(reader["CustomerName"]); } reader.Close();

Real-world example (ShopNest)

For large order exports, ShopNest uses SqlDataReader (forward-only, fast). DataSet is heavier and mainly for disconnected editing scenarios.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: dapter.Fill(dataset, "Customers"); // Fills the DataSet with data from the "Customers" table dapter.Fill(dataset, "Customers"); // Fills the DataSet with data from the "Customers" table dapter.Fill(dataset, "Customers"); // Fills the DataSet with data from the "Customers" table dapter.Fill(dataset, "Customers"); // Fills the DataSet with data from the…

Real-world example (ShopNest)

ShopNest opens a SqlConnection only for the query, then disposes it (using). Connection pooling reuses physical connections automatically.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: The Fill() method of the DataAdapter is used to populate a DataSet or DataTable with data from the database. It executes the SELECT query defined in the DataAdapter and fills the specified DataSet or DataTable with the results.

Example code

SqlDataAdapter adapter = new SqlDataAdapter("SELECT * FROM Customers", connection); DataSet dataset = new DataSet(); adapter.Fill(dataset, "Customers"); // Fills the DataSet with data from the "Customers" table

Real-world example (ShopNest)

ShopNest’s reporting job still uses ADO.NET for a heavy SQL query where raw performance and stored procedures matter more than EF convenience.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: In ADO.NET, database connections are managed using the Connection object, such as SqlConnection for SQL Server. The process involves:

Real-world example (ShopNest)

ShopNest opens a SqlConnection only for the query, then disposes it (using). Connection pooling reuses physical connections automatically.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: To execute a stored procedure using ADO.NET:

Real-world example (ShopNest)

ShopNest’s reporting job still uses ADO.NET for a heavy SQL query where raw performance and stored procedures matter more than EF convenience.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: DataSet is a collection of DataTable objects, and it can hold multiple tables and relationships between them.

Explain a bit more

It is used for handling disconnected data and can work offline, and it can also support complex structures, such as parent-child relationships. DataTable represents a single table in-memory and contains rows and columns. It can be used for simpler scenarios where only one table of data is needed. Example: DataSet: Holds multiple tables, such as Customers and Orders. DataTable: Holds data from a single table like Customers.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: To bind a DataTable to a GridView in ASP.NET:

Real-world example (ShopNest)

For large order exports, ShopNest uses SqlDataReader (forward-only, fast). DataSet is heavier and mainly for disconnected editing scenarios.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: ADO.NET exceptions are typically handled using try-catch blocks. This helps to capture any errors during database operations such as connection failures, query issues, or command execution errors. Example: try { SqlConnection connection = new SqlConnection(connectionString); connection.Open(); SqlCommand command = new SqlCommand("SELECT * FROM Customers", connection); SqlDataReader reader = command.ExecuteReader();

Example code

} catch (SqlException ex) { Console.WriteLine("Database error: " + ex.Message); } catch (Exception ex) { Console.WriteLine("General error: " + ex.Message); }

Real-world example (ShopNest)

ShopNest’s reporting job still uses ADO.NET for a heavy SQL query where raw performance and stored procedures matter more than EF convenience.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: The SqlConnection object is responsible for opening a connection to a SQL Server database. It represents the physical connection to the data source and must be open before executing commands (like SqlCommand) or reading data (using SqlDataReader or SqlDataAdapter).

Example code

SqlConnection connection = new SqlConnection(connectionString); connection.Open(); // Execute database commands connection.Close();

Real-world example (ShopNest)

ShopNest opens a SqlConnection only for the query, then disposes it (using). Connection pooling reuses physical connections automatically.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: Strongly Typed DataSet: A DataSet that is generated from an XSD (XML Schema Definition) file, which defines the structure of the data (tables, columns, relationships).

Explain a bit more

It provides type safety and compile-time checking. Loosely Typed DataSet: A DataSet that does not have predefined schemas, meaning you access tables and columns by name at runtime. This offers flexibility but no compile-time checking. Example: Strongly Typed: You get intellisense and type safety when accessing columns. Loosely Typed: You need to access tables and columns by name as strings, without intellisense.

Real-world example (ShopNest)

For large order exports, ShopNest uses SqlDataReader (forward-only, fast). DataSet is heavier and mainly for disconnected editing scenarios.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: A transaction in ADO.NET is a sequence of database operations that are executed as a single unit. If one operation fails, all previous operations are rolled back. You can manage transactions using the SqlTransaction object. Steps:

Real-world example (ShopNest)

Placing an order updates stock and inserts the order row in one SqlTransaction—either both succeed or both roll back.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: You can execute multiple transactions sequentially by managing multiple SqlTransaction objects. Each transaction can either be committed or rolled back based on the success or failure of the operations.

Example code

SqlConnection connection = new SqlConnection(connectionString); connection.Open(); SqlTransaction transaction1 = connection.BeginTransaction(); SqlTransaction transaction2 = connection.BeginTransaction(); try { // First transaction SqlCommand command1 = new SqlCommand("UPDATE Customers SET Balance = Balance - 100", connection, transaction1); command1.ExecuteNonQuery(); transaction1.Commit(); // Advanced ADO.NET Questions

Real-world example (ShopNest)

Placing an order updates stock and inserts the order row in one SqlTransaction—either both succeed or both roll back.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: In ADO.NET, the Command object is used to execute SQL queries or stored procedures. The main types of Command objects are:

Real-world example (ShopNest)

Always pass order ids with parameters: cmd.Parameters.AddWithValue("@id", orderId). Never concatenate user input into SQL.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: ADO.NET? ADO.NET supports asynchronous database operations using the async and await keywords in C#. This allows the application to remain responsive while waiting for the database operation to complete. ExecuteNonQueryAsync: Executes a SQL command asynchronously. ExecuteReaderAsync: Executes a query and returns a SqlDataReader synchronously.………… ExecuteScalarAsync: Executes a query and returns a single value…

Explain a bit more

asynchronously. public async Task GetDataAsync() { SqlConnection connection = new SqlConnection(connectionString); wait connection.OpenAsync(); SqlCommand command = new SqlCommand("SELECT * FROM Customers", connection); SqlDataReader reader = await command.ExecuteReaderAsync(); while (await reader.ReadAsync()) { Console.WriteLine(reader["CustomerName"].ToString()); } reader.Close(); } ADO.NET? ADO.NET supports asynchronous database operations using the async and await keywords in C#. This allows the application to remain responsive while waiting for the database operation to complete. ExecuteNonQueryAsync: Executes a SQL command asynchronously. ExecuteReaderAsync: Executes a query and returns a SqlDataReader synchronously.…… ExecuteScalarAsync: Executes a query and returns a single value asynchronously.

Example code

public async Task GetDataAsync() { SqlConnection connection = new SqlConnection(connectionString); wait connection.OpenAsync(); SqlCommand command = new SqlCommand("SELECT * FROM Customers", connection); SqlDataReader reader = await command.ExecuteReaderAsync(); while (await reader.ReadAsync()) { Console.WriteLine(reader["CustomerName"].ToString()); } reader.Close(); }

Real-world example (ShopNest)

ShopNest’s reporting job still uses ADO.NET for a heavy SQL query where raw performance and stored procedures matter more than EF convenience.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: ADO.NET supports asynchronous database operations using the async and await keywords in C#.

Explain a bit more

This allows the application to remain responsive while waiting for the database operation to complete. ExecuteNonQueryAsync: Executes a SQL command asynchronously. ExecuteReaderAsync: Executes a query and returns a SqlDataReader asynchronously. ExecuteScalarAsync: Executes a query and returns a single value asynchronously. Example: public async Task GetDataAsync()

Example code

{
SqlConnection connection = new SqlConnection(connectionString);
await connection.OpenAsync(); SqlCommand command = new SqlCommand("SELECT * FROM Customers", connection); SqlDataReader reader = await command.ExecuteReaderAsync(); while (await reader.ReadAsync()) { Console.WriteLine(reader["CustomerName"].ToString()); } reader.Close(); }

Real-world example (ShopNest)

ShopNest’s reporting job still uses ADO.NET for a heavy SQL query where raw performance and stored procedures matter more than EF convenience.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: ADO.NET. A stored procedure is a precompiled set of SQL statements that are stored and executed on the database server. They can improve performance and security by encapsulating complex operations. In ADO.NET, stored procedures are executed using the SqlCommand object, where the CommandType property is set to CommandType.StoredProcedure.

Example code

SqlCommand command = new SqlCommand("GetCustomerDetails", connection); command.CommandType = CommandType.StoredProcedure; command.Parameters.AddWithValue("@CustomerID", customerId); SqlDataReader reader = command.ExecuteReader();

Real-world example (ShopNest)

ShopNest’s reporting job still uses ADO.NET for a heavy SQL query where raw performance and stored procedures matter more than EF convenience.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: way to safely and securely inject data into queries, reducing the risk of SQL injection ttacks.

Explain a bit more

In ADO.NET, you handle parameters using the Parameters collection of a SqlCommand object. way to safely and securely inject data into queries, reducing the risk of SQL injection ttacks. In ADO.NET, you handle parameters using the Parameters collection of a SqlCommand object. way to safely and securely inject data into queries, reducing the risk of SQL injection ttacks. In ADO.NET, you handle parameters using the Parameters collection of a SqlCommand object. SqlCommand command = new SqlCommand("SELECT * FROM Customers WHERE CustomerID = @CustomerID", connection); command.Parameters.AddWithValue("@CustomerID", customerId); way to safely and securely inject data into queries, reducing the risk of SQL injection ttacks. In ADO.NET, you handle parameters using the Parameters collection of a SqlCommand object.

Example code

SqlCommand command = new SqlCommand("SELECT * FROM Customers WHERE CustomerID = @CustomerID", connection); command.Parameters.AddWithValue("@CustomerID", customerId);

Real-world example (ShopNest)

Always pass order ids with parameters: cmd.Parameters.AddWithValue("@id", orderId). Never concatenate user input into SQL.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: Parameters are used to pass values to SQL commands or stored procedures. They provide a way to safely and securely inject data into queries, reducing the risk of SQL injection attacks. In ADO.NET, you handle parameters using the Parameters collection of a SqlCommand object.

Example code

SqlCommand command = new SqlCommand("SELECT * FROM Customers WHERE CustomerID = @CustomerID", connection); command.Parameters.AddWithValue("@CustomerID", customerId);

Real-world example (ShopNest)

Always pass order ids with parameters: cmd.Parameters.AddWithValue("@id", orderId). Never concatenate user input into SQL.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: SQL injection attacks can be prevented by:

Real-world example (ShopNest)

Always pass order ids with parameters: cmd.Parameters.AddWithValue("@id", orderId). Never concatenate user input into SQL.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: snapshot of the data and remains unchanged even if the data in the database changes during the operation. It is slower and consumes more memory compared to forward-only cursor.

Real-world example (ShopNest)

ShopNest’s reporting job still uses ADO.NET for a heavy SQL query where raw performance and stored procedures matter more than EF convenience.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: Forward-only cursor: A cursor that allows you to read rows sequentially in a forward direction only.

Explain a bit more

It is fast and lightweight, but you cannot go back to previous rows. Static cursor: A cursor that allows both forward and backward navigation. It provides a snapshot of the data and remains unchanged even if the data in the database changes during the operation. It is slower and consumes more memory compared to a forward-only cursor.

Real-world example (ShopNest)

ShopNest’s reporting job still uses ADO.NET for a heavy SQL query where raw performance and stored procedures matter more than EF convenience.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: An ADO.NET DataProvider is a set of classes used to interact with different types of data sources (such as SQL Server, Oracle, etc.). It provides methods for opening connections, executing commands, and retrieving data. The main types of DataProviders are: SqlClient (for SQL Server) OleDb (for OLE DB-compatible data sources) Odbc (for ODBC-compatible data sources) Oracle (for Oracle databases)

Real-world example (ShopNest)

ShopNest’s reporting job still uses ADO.NET for a heavy SQL query where raw performance and stored procedures matter more than EF convenience.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: llows you to define the name, data type, size, and value of a parameter.

Explain a bit more

SqlParameter is used to protect against SQL injection and to pass data to SQL queries safely. llows you to define the name, data type, size, and value of a parameter. SqlParameter is used to protect against SQL injection and to pass data to SQL queries safely. llows you to define the name, data type, size, and value of a parameter. SqlParameter is used to protect against SQL injection and to pass data to SQL queries safely. SqlCommand command = new SqlCommand("SELECT * FROM Customers WHERE CustomerID = @CustomerID", connection); SqlParameter parameter = new SqlParameter("@CustomerID", SqlDbType.Int); parameter.Value = customerId; command.Parameters.Add(parameter); llows you to define the name, data type, size, and value of a parameter. SqlParameter is used to protect against SQL injection and to pass data to SQL queries safely.

Example code

SqlCommand command = new SqlCommand("SELECT * FROM Customers WHERE CustomerID = @CustomerID", connection); SqlParameter parameter = new SqlParameter("@CustomerID", SqlDbType.Int); parameter.Value = customerId; command.Parameters.Add(parameter);

Real-world example (ShopNest)

Always pass order ids with parameters: cmd.Parameters.AddWithValue("@id", orderId). Never concatenate user input into SQL.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: The SqlParameter class represents a parameter to a SQL command or stored procedure. It allows you to define the name, data type, size, and value of a parameter. SqlParameter is used to protect against SQL injection and to pass data to SQL queries safely.

Example code

SqlCommand command = new SqlCommand("SELECT * FROM Customers WHERE CustomerID = @CustomerID", connection); SqlParameter parameter = new SqlParameter("@CustomerID", SqlDbType.Int); parameter.Value = customerId; command.Parameters.Add(parameter);

Real-world example (ShopNest)

Always pass order ids with parameters: cmd.Parameters.AddWithValue("@id", orderId). Never concatenate user input into SQL.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.