Q1. What is ADO.NET Entity Framework?
Answer
ADO.NET Entity Framework is an open-source Object-Relational Mapping (ORM) framework that allows developers to work with databases using .NET objects. It enables querying the database in an object-oriented fashion.
Q2. What are the benefits of using Entity Framework?
Answer
Entity Framework simplifies data access, reduces development time, supports LINQ queries, and provides features like change tracking and lazy loading.
Q3. What is a DbContext in Entity Framework?
Answer
DbContext is the primary class that coordinates Entity Framework functionality for a given data model. It manages the entity objects during runtime, including populating them with data from the database, change tracking, and persisting data to the database.
Q4. Explain the difference between Code-First and Database-First approaches.
Answer
In the Code-First approach, the model classes are written first, and the database is generated from these classes. In the Database-First approach, the database is created first, and the model classes are generated from the existing database.
Q5. What is Lazy Loading in Entity Framework?
Answer
Lazy Loading is a design pattern used in Entity Framework to defer the loading of related data until it is needed. It helps in improving performance by loading data on demand.
Q6. What are POCO classes in Entity Framework?
Answer
POCO (Plain Old CLR Objects) classes are simple classes that do not depend on any specific framework. They are used in Entity Framework to represent data models without inheriting from any base class.
Q7. What is the purpose of Migrations in Entity Framework?
Answer
Migrations in Entity Framework allow you to incrementally update the database schema to keep it in sync with the data model while preserving existing data.
Q8. What is the difference between Entity Framework and ADO.NET?
Answer
Entity Framework is an ORM that provides a higher level of abstraction over ADO.NET, allowing developers to work with data using .NET objects and LINQ queries. ADO.NET is a lower-level data access technology that requires more manual coding.
Q9. What is a Navigation Property in Entity Framework?
Answer
A Navigation Property is a property in an entity class that represents a relationship to another entity. It allows you to navigate from one entity to a related entity.
Q10. What is the purpose of the Fluent API in Entity Framework?
Answer
The Fluent API in Entity Framework provides a way to configure the data model using code instead of attributes. It is more flexible and powerful than data annotations.
Intermediate Questions
Q11. How do you handle concurrency in Entity Framework?
Answer
Concurrency in Entity Framework can be handled using concurrency tokens, such as a timestamp or a version column, to detect changes made by other users.
Q12. What is the purpose of the Include method in Entity Framework?
Answer
The Include method is used to eagerly load related data in a single query. It helps in improving performance by reducing the number of database queries.
Q13. What are the different states of an entity in Entity Framework?
Answer
The different states of an entity in Entity Framework are Added, Unchanged, Modified, Deleted, and Detached.
Q14. What is the purpose of the AsNoTracking method in Entity Framework?
Answer
The AsNoTracking method is used to query data without tracking changes. It improves performance by reducing memory usage and avoiding the overhead of change tracking.
Q15. What is the difference between IQueryable and IEnumerable in Entity Framework?
Answer
IQueryable is used for querying data from the database and supports deferred execution. IEnumerable is used for querying data in memory and supports immediate execution.
Q16. What is the purpose of the ToList method in Entity Framework?
Answer
The ToList method is used to execute a query and return the results as a list. It forces immediate execution of the query and loads all the data into memory.
Q17. What is the purpose of the AddRange method in Entity Framework?
Answer
The AddRange method is used to add multiple entities to the context in a single call. It is more efficient than adding entities one by one.
Q18. What is the purpose of the Find method in Entity Framework?
Answer
The Find method is used to retrieve an entity by its primary key. It first checks the local cache and then queries the database if the entity is not found in the cache.
Q19. What is the purpose of the SaveChanges method in Entity Framework?
Answer
The SaveChanges method is used to persist changes made to the entities in the context to the database. It saves all the changes in a single transaction.
Q20. What is the purpose of the Entry method in Entity Framework?
Answer
The Entry method is used to access the change tracking information for an entity. It provides methods to mark an entity as modified, deleted, or unchanged.
Advanced Questions
Q21. What is the purpose of the AsQueryable method in Entity Framework?
Answer
The AsQueryable method is used to convert an IEnumerable to an IQueryable. It allows further composition of queries using LINQ methods.
Q22. What is the purpose of the AsParallel method in Entity Framework?
Answer
The AsParallel method is used to enable parallel execution of a query. It can improve performance by utilizing multiple CPU cores.
Q23. What is the purpose of the AsStreaming method in Entity Framework?
Answer
The AsStreaming method is used to enable streaming of query results. It allows processing of data as it is being read from the database, reducing memory usage.
Q24. What is the purpose of the AsTracking method in Entity Framework?
Answer
The AsTracking method is used to enable change tracking for a query. It allows Entity Framework to track changes made to the entities returned by the query.
Q25. What is the purpose of the FromSqlRaw method in Entity Framework?
Answer
The FromSqlRaw method is used to execute raw SQL queries and map the results to entity types. It provides a way to use custom SQL queries with Entity Framework.
Q26. What is the purpose of the FromSqlInterpolated method in Entity Framework?
Answer
The FromSqlInterpolated method is used to execute raw SQL queries with interpolated strings. It provides a way to use custom SQL queries with parameterized values.
Q27. What is the purpose of the ExecuteSqlRaw method in Entity Framework?
Answer
The ExecuteSqlRaw method is used to execute raw SQL commands that do not return results. It is useful for executing commands like INSERT, UPDATE, or DELETE.
Q28. What is the purpose of the ExecuteSqlInterpolated method in Entity Framework?
Answer
The ExecuteSqlInterpolated method is used to execute raw SQL commands with interpolated strings. It provides a way to use custom SQL commands with parameterized values.
Q29. What is the purpose of the ToQueryString method in Entity Framework?
Answer
The ToQueryString method is used to generate the SQL query string for a LINQ query. It is useful for debugging and understanding the generated SQL.
Q30. What is the purpose of the ToParameterList method in Entity Framework?
Answer
The ToParameterList method is used to generate a list of parameters for a raw SQL query. It is useful for executing parameterized SQL queries.
Performance and Optimization Questions
Q31. How do you optimize performance in Entity Framework?
Answer
Performance in Entity Framework can be optimized by using eager loading, disabling change tracking, using AsNoTracking, minimizing the number of database queries, and using compiled queries.
Q32. What is the purpose of compiled queries in Entity Framework?
Answer
Compiled queries in Entity Framework are used to cache the execution plan of a query. They improve performance by reducing the overhead of query compilation.
Q33. What is the purpose of the UseQueryTrackingBehavior method in Entity Framework?
Answer
The UseQueryTrackingBehavior method is used to configure the default query tracking behavior for a DbContext. It allows enabling or disabling change tracking for all queries.
Q34. What is the purpose of the UseLazyLoadingProxies method in Entity Framework?
Answer
The UseLazyLoadingProxies method is used to enable lazy loading for navigation properties. It allows loading related data on demand.
Q35. What is the purpose of the UseSqlServer method in Entity Framework?
Answer
The UseSqlServer method is used to configure Entity Framework to use SQL Server as the database provider. It allows specifying the connection string and other options.
Security Questions
Q36. How do you handle SQL injection attacks in Entity Framework?
Answer
Entity Framework provides built-in protection against SQL injection attacks by using parameterized queries. It ensures that user input is treated as data and not executable code.
Q37. What is the purpose of the HasData method in Entity Framework?
Answer
The HasData method is used to seed data in the database. It allows specifying initial data for a table when the database is created.
Q38. What is the purpose of the HasIndex method in Entity Framework?
Answer
The HasIndex method is used to create an index on a column or a set of columns. It improves query performance by allowing faster data retrieval.
Q39. What is the purpose of the HasCheckConstraint method in Entity Framework?
Answer
The HasCheckConstraint method is used to create a check constraint on a column. It ensures that the data in the column meets specific criteria.
Q40. What is the purpose of the HasDefaultValue method in Entity Framework?
Answer
The HasDefaultValue method is used to set a default value for a column. It ensures that the column has a default value when a new row is inserted.
Best Practices Questions
Q41. What are the best practices for using Entity Framework?
Answer
Best practices for using Entity Framework include using navigation properties for relationships, using data annotations or Fluent API for configuration, minimizing the use of lazy loading, and using asynchronous methods for database operations.
Q42. What is the purpose of the AsAsyncEnumerable method in Entity Framework?
Answer
The AsAsyncEnumerable method is used to enable asynchronous streaming of query results. It allows processing of data as it is being read from the database without blocking the calling thread.
Q43. What is the purpose of the ToListAsync method in Entity Framework?
Answer
The ToListAsync method is used to execute a query asynchronously and return the results as a list. It improves performance by not blocking the calling thread.
Q44. What is the purpose of the FirstOrDefaultAsync method in Entity Framework?
Answer
The FirstOrDefaultAsync method is used to execute a query asynchronously and return the first element or a default value if no element is found. It improves performance by not blocking the calling thread.
Q45. What is the purpose of the SingleOrDefaultAsync method in Entity Framework?
Answer
The SingleOrDefaultAsync method is used to execute a query asynchronously and return the single element or a default value if no element is found. It improves performance by not blocking the calling thread.
Troubleshooting Questions
Q46. How do you troubleshoot performance issues in Entity Framework?
Answer
Performance issues in Entity Framework can be troubleshot by profiling queries, analyzing execution plans, identifying N+1 query problems, and optimizing database indexes.
Q47. What is the purpose of the EnableSensitiveDataLogging method in Entity Framework?
Answer
The EnableSensitiveDataLogging method is used to enable logging of sensitive data, such as parameter values, in Entity Framework. It is useful for debugging but should be used with caution.
Q48. What is the purpose of the EnableDetailedErrors method in Entity Framework?
Answer
The EnableDetailedErrors method is used to enable detailed error messages in Entity Framework. It is useful for debugging but should be disabled in production environments.
Q49. What is the purpose of the UseLoggerFactory method in Entity Framework?
Answer
The UseLoggerFactory method is used to configure a custom logger factory for Entity Framework. It allows logging of Entity Framework operations to a custom logging provider.
Q50. What is the purpose of the UseQueryTrackingBehavior method in Entity Framework?
Answer
The UseQueryTrackingBehavior method is used to configure the default query tracking behavior for a DbContext. It allows enabling or disabling change tracking for all queries.
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