What is the difference between the ExecuteReader() and ExecuteScalar() methods in ADO.NET when executing a SELECT statement?
- ExecuteReader() and ExecuteScalar() both return a SqlDataReader object.
- ExecuteReader() and ExecuteScalar() both return a single value from the result set.
- ExecuteReader() returns a SqlDataReader object that allows forward-only access to the result set, while ExecuteScalar() returns a single value from the first column of the first row of the result set.
- ExecuteReader() returns a single value from the first column of the first row of the result set, while ExecuteScalar() returns a SqlDataReader object that allows forward-only access to the result set.
ExecuteReader() and ExecuteScalar() are both methods in ADO.NET used to execute SELECT statements, but they differ in their return types and functionalities. ExecuteReader() returns a SqlDataReader object, which allows you to iterate through the result set row by row, while ExecuteScalar() returns a single value from the first column of the first row of the result set. This distinction is crucial when dealing with queries that return multiple rows or single values.
One-to-One relationships in Entity Framework can be mapped using the ___________ attribute.
- [ForeignKey]
- [InverseProperty]
- [OneToOne]
- [Table]
In Entity Framework, the [InverseProperty] attribute is utilized to define one-to-one relationships between entities, specifying the navigation property on the dependent entity.
Explain the concept of optimistic concurrency in LINQ to SQL.
- It's a technique where a pessimistic approach is taken, and data is locked when being accessed for modification to avoid conflicts.
- It's a technique where data is constantly checked for consistency during read operations, ensuring no conflicts occur during write operations.
- It's a technique where data is duplicated across multiple servers to ensure redundancy and fault tolerance.
- It's a technique where multiple users can simultaneously access and modify data without locking it, but conflicts are resolved when saving changes to the database.
Optimistic concurrency in LINQ to SQL is a technique where multiple users can simultaneously access and modify data without locking it. Conflicts are resolved when saving changes to the database.
The Code-First approach in Entity Framework focuses on creating the database ___________ based on entity classes.
- Schema
- Schema Structure
- Schema and Data
- Structure
The Code-First approach in Entity Framework involves creating the database schema based on the entity classes defined in the code. It allows developers to define the structure of the database using classes and relationships in their code without having to create the database manually.
In Entity Framework, what is an entity?
- A class used for styling HTML elements
- A function that performs database operations
- A query used to retrieve data from the database
- An object representing data stored in the database
In Entity Framework, an entity is an object representing data stored in the database. It typically corresponds to a table in the database, and each instance of an entity represents a row in that table. Entities are used to perform CRUD (Create, Read, Update, Delete) operations on the underlying data.
Scenario: You are building a high-performance application that requires reading a large dataset from a database. How can you efficiently achieve this using a data reader?
- Use DataSet to retrieve the entire dataset at once and then process it in memory, ensuring faster access to data without repeated database calls.
- Use Entity Framework for object-relational mapping, which abstracts the database interactions and provides a more intuitive way to work with data but may introduce overhead in high-performance scenarios.
- Use LINQ to SQL for querying the database, enabling seamless integration of database operations with C# code, but may not be as efficient for large datasets as SqlDataReader.
- Use SqlDataReader with the appropriate SQL query and optimize database interactions by fetching only the necessary columns and rows, minimizing network overhead.
By utilizing SqlDataReader along with optimized SQL queries, you can efficiently retrieve large datasets from the database while minimizing network overhead and memory consumption. Other approaches like using DataSet or Entity Framework may introduce additional overhead or may not be as efficient for high-performance scenarios compared to SqlDataReader.
Which Entity Framework feature allows you to define the structure of your database in code?
- Code-First
- Database-First
- Model-First
- Schema-First
Code-First is an Entity Framework feature that allows developers to define the structure of the database using code, typically through the use of Plain Old CLR Objects (POCO) classes. With Code-First approach, developers define their domain classes first and then generate the database schema from these classes. It offers flexibility and control over the database design and is suitable for scenarios where developers prefer to work primarily with code rather than visual designers.
LINQ to Objects is primarily used for querying data from ___________.
- Arrays
- Collections
- Databases
- XML
LINQ to Objects is used for querying in-memory data structures such as collections, arrays, or XML. It provides a convenient way to query and manipulate data.
What is the primary purpose of modifying data in datasets?
- To delete data
- To insert data
- To read data
- To update data
Modifying data in datasets primarily involves updating existing data to reflect changes made by users or applications. This can include changing values, correcting errors, or adding new information. Updating data ensures that the dataset remains accurate and up-to-date with the latest information.
The Rollback method in ADO.NET is used to ___________ a transaction.
- Abort
- Begin
- Commit
- Undo
The Rollback method in ADO.NET is used to undo or cancel a transaction, reverting any changes made since the transaction began.