Interview Q&A

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.

Short answer: The TransactionScope class in ADO.NET is used to handle distributed transactions across multiple data sources (e.g., SQL Server and other databases). It simplifies transaction management by automatically handling the commit and rollback of transactions across multiple resources.

Example code

using (TransactionScope scope = new TransactionScope()) { SqlConnection connection1 = new SqlConnection(connectionString1); SqlConnection connection2 = new SqlConnection(connectionString2); connection1.Open(); connection2.Open(); // Execute commands on both connections scope.Complete(); // Commit the transaction if everything is successful }

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.UpdateCommand = new SqlCommand("UPDATE Customers SET Name = @Name WHERE CustomerID = @CustomerID", connection); dapter.UpdateCommand.Parameters.Add("@Name", SqlDbType.NVarChar, 100, "Name"); dapter.UpdateCommand.Parameters.Add("@CustomerID", SqlDbType.Int, 4, "CustomerID"); dapter.UpdateCommand = new SqlCommand("UPDATE… Customers SET Name = @Name…… WHERE CustomerID = @CustomerID", connection);…

Explain a bit more

dapter.UpdateCommand.Parameters.Add("@Name", SqlDbType.NVarChar, 100, "Name"); dapter.UpdateCommand.Parameters.Add("@CustomerID", SqlDbType.Int, 4, "CustomerID"); dapter.UpdateCommand = new SqlCommand("UPDATE Customers SET Name = @Name WHERE CustomerID = @CustomerID", connection); dapter.UpdateCommand.Parameters.Add("@Name", SqlDbType.NVarChar, 100, "Name"); dapter.UpdateCommand.Parameters.Add("@CustomerID", SqlDbType.Int, 4, "CustomerID"); dapter.UpdateCommand = new SqlCommand("UPDATE… Customers SET Name = @Name WHERE CustomerID = @CustomerID", connection); dapter.UpdateCommand.Parameters.Add("@Name", SqlDbType.NVarChar, 100, "Name");…

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 UpdateCommand property of the DataAdapter specifies the SQL command used to update the database when changes are made to the data in the DataSet. The Update() method of the DataAdapter uses the UpdateCommand to push changes back to the database.

Example code

SqlDataAdapter adapter = new SqlDataAdapter("SELECT * FROM Customers", connection); adapter.UpdateCommand = new SqlCommand("UPDATE Customers SET Name = @Name WHERE CustomerID = @CustomerID", connection); adapter.UpdateCommand.Parameters.Add("@Name", SqlDbType.NVarChar, 100, "Name"); adapter.UpdateCommand.Parameters.Add("@CustomerID", SqlDbType.Int, 4, "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: Data-Bound Controls: These controls automatically bind to a data source, such as a DataSet or DataTable, and update the UI when the data changes. Examples include GridView, DropDownList, and ListBox. Manually Bound Controls: These controls do not automatically update when the data changes. You need to manually manage data binding, such as updating the display values when the data changes.

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 DataReader is more efficient than DataSet when dealing with large result sets because it reads data in a forward-only, read-only manner, without storing the entire result set in memory. This results in better performance and lower memory consumption.

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 DataRelation defines a relationship between two DataTable objects in a DataSet. It is used to enforce referential integrity and allows for navigating between related data in a parent-child relationship.

Example code

DataRelation relation = new DataRelation("ParentChild", parentTable.Columns["ID"], childTable.Columns["ParentID"]); dataSet.Relations.Add(relation);

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 ExecuteScalar method in ADO.NET is used to execute a query that returns a single value, typically an aggregate value like a count, sum, or average, or a single field from a row.

Explain a bit more

This method is ideal when you expect a single value as the result, rather than a set of rows. : It returns the first column of the first row in the result set. Any other columns or rows are ignored. It is commonly used for queries that return a single value (e.g., COUNT(), MAX(), MIN()).

Example code

SqlCommand command = new SqlCommand("SELECT COUNT(*) FROM Customers", connection); connection.Open(); int customerCount = (int)command.ExecuteScalar(); Console.WriteLine("Number of customers: " + customerCount); In this example, ExecuteScalar returns the number of rows in the Customers table.

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: And columns, and it is used to hold data returned from the database. Key Features: Can hold data from one table. view.RowFilter = "Name = 'Alice'"; view.Sort = "ID DESC"; Summary: DataTable holds data, and DataView provides a dynamic view (filtering, sorting) of the DataTable.

Example code

And columns, and it is used to hold data returned from the database. Key Features: Can hold data from one table. view.RowFilter = "Name = 'Alice'";
view.Sort = "ID DESC"; Summary: DataTable holds data, and DataView provides a dynamic view (filtering, sorting) of the DataTable.

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: Both DataTable and DataView are used to represent data in ADO.NET, but they have different purposes: DataTable: Represents a single table of data in-memory.

Explain a bit more

It is a container for rows and columns, and it is used to hold data returned from the database. Key Features: Can hold data from one table. Provides methods for data manipulation (e.g., adding, deleting, modifying rows). Can be filled with data from a DataAdapter. Example: DataTable table = new DataTable(); table.Columns.Add("ID"); table.Columns.Add("Name"); table.Rows.Add(1, "Alice"); table.Rows.Add(2, "Bob"); ● DataView: Provides a way to view and filter data from a DataTable without changing the underlying data. It allows you to sort and filter the data dynamically. Key Features: Acts as a view of a DataTable. Allows for sorting, filtering, and searching the data. It does not modify the underlying DataTable. Example: DataView view = new DataView(table);

Example code

view.RowFilter = "Name = 'Alice'";
view.Sort = "ID DESC"; Summary: DataTable holds data, and DataView provides a dynamic view (filtering, sorting) of the DataTable.

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 BatchUpdate method is used to send multiple SQL commands (such as insert, update, or delete) in a single round trip to the database.

Explain a bit more

This improves performance by reducing the overhead of sending multiple individual commands. While BatchUpdate isn't directly exposed as a method on the DataAdapter object, you can achieve similar functionality by manually creating a batch of commands and executing them in a single call. Example (Using SqlDataAdapter): SqlDataAdapter adapter = new SqlDataAdapter("SELECT * FROM Customers", connection); SqlCommandBuilder builder = new SqlCommandBuilder(adapter); // Automatically generates commands for Update, Insert, and Delete DataTable table = new DataTable(); adapter.Fill(table); // Modify DataTable as needed // Update changes to the database in one go (BatchUpdate) adapter.Update(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.