1. What is Entity Framework (EF)?
- Answer: Entity Framework is an Object-Relational Mapping (ORM) framework in .NET that simplifies database interactions by allowing developers to work with databases using .NET objects.
2. What are the main components of Entity Framework?
- Answer: The main components of Entity Framework include:
- Entity Data Model
- Object Services
- LINQ to Entities
- Entity SQL
3. Explain the Entity Data Model (EDM).
- Answer: EDM is a conceptual model that defines the structure of the data and the relationships between entities. It includes Entity Types, Associations, and Entity Containers.
4. What is Code-First in Entity Framework?
- Answer: Code-First is an approach in Entity Framework where the database is created based on the classes (code) rather than creating classes based on an existing database schema.
5. Explain the Database-First approach in Entity Framework.
- Answer: Database-First is an approach in Entity Framework where the entity data model is created from an existing database schema. The classes are generated based on the database tables.
6. What is the Model-First approach in Entity Framework?
- Answer: Model-First is an approach in Entity Framework where the Entity Data Model is created visually using the Entity Framework Designer in Visual Studio. The database schema and classes are generated from the model.
7. What is an Entity in Entity Framework?
- Answer: An entity in Entity Framework is a class that represents a database table or view. Each instance of the class corresponds to a row in the table.
8. What is a DbContext in Entity Framework?
- Answer: DbContext is a primary class in Entity Framework that represents a session with the database. It is responsible for coordinating Entity Framework functionality for a data model.
9. Explain the role of DbSet in Entity Framework.
- Answer: DbSet represents an entity set that can be queried and updated in a database. It is a property of DbContext and corresponds to a table in the database.
10. What is Lazy Loading in Entity Framework? - Answer: Lazy Loading is a feature in Entity Framework that loads related entities from the database only when they are accessed for the first time. It helps in improving performance by loading data on-demand.
11. How can you disable Lazy Loading in Entity Framework?
- Answer: Lazy Loading can be disabled by setting the LazyLoadingEnabled property of the DbContext to false.
12. Explain Eager Loading in Entity Framework.
- Answer: Eager Loading is a technique in Entity Framework to load related entities along with the main entity in a single database query. This is achieved using the Include method or ThenInclude method for complex types.
13. What is the purpose of the Entity Framework Power Tools? - Answer: Entity Framework Power Tools is a Visual Studio extension that allows developers to view the database schema, generate Code-First classes from an existing database, and perform other Entity Framework-related tasks.
14. What is the role of Migration in Entity Framework? - Answer: Migrations in Entity Framework allow developers to evolve the database schema over time. They provide a way to update the database to match changes in the model.
15. How can you enable migrations in Entity Framework Code-First?
- Answer: Migrations can be enabled using the Enable-Migrations command in the Package Manager Console.
16. Explain the purpose of the Add-Migration and Update-Database commands.
- Answer: Add-Migration is used to scaffold a new migration based on the changes detected in the model, and Update-Database is used to apply pending migrations to the database.
17. What is the difference between SaveChanges and SaveChangesAsync in Entity Framework?
- Answer: SaveChanges is a synchronous method that saves changes to the database, while SaveChangesAsync is an asynchronous method that allows asynchronous saving of changes.
18. How does Entity Framework handle concurrency? - Answer: Entity Framework handles concurrency using optimistic concurrency. It checks if the data being updated has been modified by another user since it was queried. If changes are detected, an exception is thrown.
19. What is the purpose of the Database.Log property in Entity Framework?
- Answer: Database.Log is a property in Entity Framework that allows developers to log SQL statements and other information generated by Entity Framework. It is useful for debugging and performance optimization.
20. Explain the concept of Database Initialization in Entity Framework. - Answer: Database Initialization is the process of creating and seeding a database. Entity Framework supports different initialization strategies, including CreateDatabaseIfNotExists, DropCreateDatabaseIfModelChanges, and DropCreateDatabaseAlways.
21. What is a Database Seeder in Entity Framework? - Answer: A Database Seeder is a class or method in Entity Framework that populates the database with initial or test data. It is often used in combination with database initialization strategies.
22. How can you execute raw SQL queries in Entity Framework?
- Answer: Raw SQL queries can be executed using the SqlQuery method in Entity Framework. It allows developers to execute SQL commands and retrieve results as entities.
23. Explain the purpose of the AsNoTracking method in Entity Framework.
- Answer: The AsNoTracking method in Entity Framework disables tracking of entities, which can improve performance for read-only scenarios where entities are not going to be modified.
24. How does Entity Framework handle transactions?
- Answer: Entity Framework supports transactions using the TransactionScope class. Transactions can be used to group multiple operations into a single atomic unit.
25. What is the Inheritance Mapping strategy in Entity Framework? - Answer: Inheritance Mapping is a strategy
in Entity Framework for modeling inheritance in object-oriented programming within a relational database. It includes Table-per-Hierarchy (single table), Table-per-Type (one table per concrete type), and Table-per-Concrete Class (one table per concrete class).
26. How can you disable automatic detection of changes in Entity Framework?
- Answer: Automatic change detection can be disabled using the Configuration.AutoDetectChangesEnabled property set to false.
27. What is the purpose of the Include method in Entity Framework queries?
- Answer: The Include method is used to specify related entities that should be included in the result of a query, preventing the need for additional database round-trips.
28. How can you improve performance when dealing with large datasets in Entity Framework? - Answer: Performance can be improved by using techniques such as projection (selecting only required columns), paginating results, disabling change tracking, and using appropriate indexes in the database.
29. What is the Repository Pattern, and how can it be implemented with Entity Framework? - Answer: The Repository Pattern is a design pattern that separates the logic that retrieves data from the underlying storage system. It can be implemented with Entity Framework by creating repositories that encapsulate data access logic.
30. Explain the N+1 Query Problem in Entity Framework. - Answer: The N+1 Query Problem occurs when a query fetches a collection of entities along with their related entities, resulting in a separate query for each related entity. This can lead to performance issues.
31. How can you address the N+1 Query Problem in Entity Framework?
- Answer: The N+1 Query Problem can be addressed by using Eager Loading (Include method), Explicit Loading (Load method), or Projection (selecting only required data).
32. What is the purpose of the ConcurrencyCheck attribute in Entity Framework?
- Answer: The ConcurrencyCheck attribute is used to indicate that a property should be included in optimistic concurrency checks. It helps in preventing simultaneous updates to the same entity from causing data inconsistency.
33. What is the purpose of the NotMapped attribute in Entity Framework?
- Answer: The NotMapped attribute is used to specify that a property or field should not be mapped to a column in the database. It is useful when there is a need to include a property in the entity class that doesn't correspond to a database column.
34. How can you seed an initial database using Entity Framework Code-First Migrations?
- Answer: Database seeding can be accomplished by overriding the Seed method in the DbMigrationsConfiguration class and adding code to populate the database with initial data.
35. Explain the purpose of the DatabaseGenerated attribute in Entity Framework.
- Answer: The DatabaseGenerated attribute is used to specify how values for a property are generated in the database. It can be used for identity columns, computed columns, and more.
36. What is the purpose of the Required attribute in Entity Framework?
- Answer: The Required attribute is used to specify that a property is required and must have a non-null value. It is used for enforcing constraints in the database schema.
37. How can you execute stored procedures in Entity Framework?
- Answer: Stored procedures can be executed using the Database.SqlQuery method or the DbContext.Database.ExecuteSqlCommand method in Entity Framework.
38. Explain the purpose of the OnModelCreating method in Entity Framework.
- Answer: The OnModelCreating method is part of the DbContext and is used to configure the model by applying conventions, setting configurations for entities, and defining relationships.
39. What is the purpose of the MaxLength attribute in Entity Framework?
- Answer: The MaxLength attribute is used to specify the maximum length of a string or binary property when generating the database schema.
40. How can you disable automatic migrations in Entity Framework Code-First?
- Answer: Automatic migrations can be disabled by setting the AutomaticMigrationsEnabled property to false in the Configuration class.
41. Explain the purpose of the Column attribute in Entity Framework.
- Answer: The Column attribute is used to specify the name, data type, and other properties of a column in the database when mapping entities to database tables.
42. What is the purpose of the Table attribute in Entity Framework?
- Answer: The Table attribute is used to specify the name of the table in the database when mapping an entity to a table.
43. How can you implement a many-to-many relationship in Entity Framework? - Answer: A many-to-many relationship can be implemented by creating a junction table and defining navigation properties on both ends of the relationship.
44. Explain the purpose of the ComplexType attribute in Entity Framework.
- Answer: The ComplexType attribute is used to specify that a class should be treated as a complex type rather than an entity. Complex types are classes without keys and are typically used to group related properties.
45. How does Entity Framework handle cascading delete operations?
- Answer: Entity Framework can be configured to perform cascading delete operations using the Cascade option in the DeleteBehavior property of a foreign key relationship.
46. What is the purpose of the StringLength attribute in Entity Framework?
- Answer: The StringLength attribute is used to specify the maximum length of a string property when generating the database schema. It is used for character columns.
47. How can you use stored procedures for Insert, Update, and Delete operations in Entity Framework?
- Answer: Entity Framework supports stored procedures for Insert, Update, and Delete operations by mapping these procedures to corresponding operations in the OnModelCreating method or using the Database.SqlQuery method.
48. Explain the purpose of the ConcurrencyMode property in Entity Framework.
- Answer: The ConcurrencyMode property is used to specify how concurrency conflicts should be handled. Possible values include None, Fixed, and Variable.
49. How can you improve performance when inserting a large number of records using Entity Framework?
- Answer: Performance can be improved by using techniques such as BulkInsert libraries, disabling change tracking, and increasing the SaveChanges performance through batching.
50. What is the purpose of the IsConcurrencyToken attribute in Entity Framework?
- Answer: The IsConcurrencyToken attribute is used to indicate that a property should be included in optimistic concurrency checks. It helps in preventing simultaneous updates to the same entity from causing data inconsistency.