Scenario: You need to insert a new customer record into a SQL Server database using LINQ to SQL. Which LINQ to SQL method or operation would you use for this task?

  • Add
  • Attach
  • InsertOnSubmit
  • Update
InsertOnSubmit method is used to insert a new record into a LINQ to SQL data context. It queues the object to be inserted upon calling the SubmitChanges method. This method is specifically designed for adding new records. The Add method is not part of LINQ to SQL; it's typically used with Entity Framework. Update is used to modify existing records, and Attach is used to attach existing objects to a data context, not for inserting new records.

ADO.NET provides ___________ classes for parameterized queries that are specific to different database providers.

  • ODBC
  • OLE DB
  • Oracle
  • SQL Server
ADO.NET provides classes such as OleDbCommand for OLE DB providers and SqlCommand for SQL Server providers, allowing developers to create parameterized queries specific to different database providers.

In LINQ to Entities, the Entity Framework uses ___________ to represent database tables.

  • Entities
  • Classes
  • Objects
  • Models
The correct option is "Entities". In LINQ to Entities, the Entity Framework maps database tables to entity classes, where each entity class represents a table in the database. These entities are used to perform operations such as querying, updating, and deleting data in the underlying database. The term "Entities" refers to these classes that are used to represent the database tables in LINQ to Entities.

Scenario: When working with Entity Framework, you want to ensure that your queries are optimal. What are some common mistakes developers should avoid when writing Entity Framework queries for performance-critical applications?

  • Ignoring database schema and table relationships
  • Neglecting to use parameterized queries for dynamic data
  • Overusing LINQ-to-Entities for complex query operations
  • Using Include method excessively for loading related entities
Excessive use of the Include method can result in fetching unnecessary data, leading to performance degradation. Ignoring database schema and relationships can lead to inefficient query execution. Parameterized queries prevent SQL injection attacks and optimize query execution. Overusing LINQ-to-Entities can result in inefficient translation of LINQ queries to SQL, impacting performance.

The DataTextField property of a DropDownList control is used to specify the ___________ of the data items to display.

  • Key
  • Label
  • Text
  • Value
The correct answer is "Text." The DataTextField property is used to specify the field from the data source that will be displayed as the text in the DropDownList control. For instance, if your data source has a "Name" field, you would set DataTextField to "Name" to display names in the DropDownList.

What is the purpose of the WHERE clause in a SELECT statement?

  • Determines the order of the result set
  • Filters the rows returned by the SELECT statement based on a specified condition
  • Groups the result set by a specified column
  • Joins multiple tables in the SELECT statement
The WHERE clause is used to filter rows returned by the SELECT statement based on a specified condition. It allows you to specify a condition that must be met for each row to be included in the result set. This condition can include comparisons, logical operators, and functions, allowing for flexible filtering of data.

When should you use a stored procedure as a command object in ADO.NET?

  • When the application needs to execute dynamic SQL queries
  • When the application needs to perform simple CRUD operations
  • When the application requires complex business logic to be executed on the database side
  • When the database schema frequently changes
Stored procedures are beneficial when the application requires complex business logic to be executed on the database side. They offer advantages such as improved performance, enhanced security, and encapsulation of business logic within the database. By using stored procedures as command objects in ADO.NET, developers can centralize and manage database logic efficiently, promoting maintainability and scalability in the application architecture.

When working with LINQ to Entities, what is eager loading, and how can it impact performance?

  • Allows lazy loading of related entities
  • Delays loading related entities until they are explicitly requested
  • Forces related entities to be loaded at the same time as the main entity
  • Preloads related entities along with the main entity to reduce additional database queries
Eager loading in LINQ to Entities preloads related entities along with the main entity to reduce additional database queries. This can significantly improve performance by minimizing the number of round trips to the database. Understanding when to use eager loading versus lazy loading is crucial for optimizing performance in LINQ to Entities.

To check for NULL values in a data reader, you can use the ___________ method.

  • CheckNull
  • IsDBNull
  • NullCheck
  • ValidateNull
In .NET, the IsDBNull method is used to check for NULL values in a data reader. This method is available on data reader objects such as SqlDataReader, OracleDataReader, and others. It returns true if the specified column contains a NULL value, allowing developers to handle NULL values appropriately in their applications. Using IsDBNull ensures data integrity and prevents errors when processing query results that may contain NULL values.

You need to retrieve data from multiple related tables in a database using a single SQL query. Which SQL clause will be crucial in this situation?

  • JOIN
  • WHERE
  • GROUP BY
  • HAVING
The correct option is JOIN. The JOIN clause is crucial for retrieving data from multiple related tables in a single SQL query. It allows you to combine rows from two or more tables based on a related column between them. Using JOINs helps in avoiding multiple queries and improves query performance.