Entity Framework Interview Questions

Entity Framework Interview Questions for Experienced

21. What are Entity Framework POCO classes?

Ans: POCO is an abbreviation for Plain Old C# Object. EDMX generated classes that are cluttered with entity tags. We frequently want to use simple.NET classes and integrate them with the Entity Framework.

22. What are the Entity Framework Architecture components?

Ans: The following are the Entity Framework components:

• Entity SQL 
• Object Service 
• Entity Data Model (EDM) 
• LINQ to Entities
• ADO.Net 
• Data Provider 
• Entity Client Data Provider

23. What is an Entity Data Model?

Ans: An entity data model (EDM), which is independent of the underlying database schema, is a conceptual representation of the data in a database. EDM is represented in Entity Framework by a collection of classes that provide the organization of entities (objects) and connections between them.

It acts as a connection point between the application and the database, enabling programmers to handle data in an object-oriented way. Entities, affiliations, and mappings between entities and the database tables are all included in this model.

24. Explain the different parts of the Entity Data Model?

Ans: There are three primary components to the entity data model (EDM):

• Conceptual Model: It illustrates how the application views the data conceptually. It describes entities (things), their attributes, and their connections with one another. In an object-oriented programming language like C# or VB.NET, it is often specified via classes
   
• Storage Model: It shows how the underlying database is organized. It consists of tables, views, keys, and other components unique to databases. By using the database schema, it is represented
   
• Mapping: These show how the conceptual model and the storage model relate to one another. It details the mapping of entities' properties to database columns and tables. This step makes sure that data is correctly stored in the database and retrieved when needed
   

25. What is LINQ to entities?

Ans: LINQ to Entities is query language which we use to write queries against the object models and the resultant query will return the entities defined in the Conceptual Model.

26. What is the EF Data Access Architecture?

Ans: The ADO.NET Framework supports two Data Access Architecture models:

• Interested in making connections
• Disconnected

EF employs the Disconnected model (no connections are left open). Because you work with data and make desired changes before performing the SaveChanges. A context in an N-tier application either creates or saves entities, but not both. It generates entities that are serialized and dispose of the context. Entities that return from the client application are deserialized and reattached to a new context instance, where their changes are saved.

27. What is the DataAdapter class in ADO.NET?

Ans: The ADO.NET data-adapter class retrieves data from a database, stores it in a dataset, and then return changes to the database. Data-adapter serves as an intermediary for all types of communication. Data-adapter fills data into a Data-table using the Fill() method.

28. What is the difference between connected and disconnected data access in ADO.NET?

Ans: Connected data access: You can have connected data access by using the DataReader objects of the data provider. It allows for quick access to data but does not allow for editing.

Disconnected data access: Disconnected data access is accomplished using the DataAdapter object. The dataset is editable and works independently of the database.

29. What exactly is Optimistic Locking?

Ans: Optimistic locking is a strategy that involves reading a record, noting a version number (other methods include dates, timestamps, or checksums/hashes), and ensuring that the version hasn't changed before writing the record back. When you write the record back, you filter the version update to ensure it's atomic. (that is, it hasn't been updated between the time you check the version and write the record to the disc) and update the version in a single hit.

If the record is dirty (i.e., a different version than yours), the transaction is aborted and the user can restart it. This strategy is best suited for high-volume systems and three-tier architectures where a connection is not always maintained.

30. What are the key functionalities offered by the Entity Framework?

Ans: The key functionalities offered by the Entity framework are Object-relational mapping, LINQ integration, change tracking, CRUD operations, Lazy loading, transactions, and database-first approaches.

31. Discover the various types of inheritance that Entity Framework supports.

Ans: There are three types of inheritance:

• Table Par Hierarchy(TPH): In this, all classes in an inheritance hierarchy are mapped to a single table. It puts all the fields for each type into a single table. After that, it uses the discriminator field to differentiate the types
   
• Table Per Type(TPT): It is similar to the TPH, but in this, each class in the inheritance has its own table
   
• Table Per Concrete Class: It creates a separate table for each concrete class and stores its fields in that separate table

32. Explain the concept of database concurrency and discover effective strategies for managing it.

Ans: Database concurrency is the ability to handle multiple concurrent transactions and it modify the data simultaneously. Below are some strategies:

• Optimistic concurrency: It assumes that conflicts are rare and each transaction reads the data without locking it. If no conflicts occur, then the changes are committed. Otherwise, it aborts the transaction
   
• Pessimistic concurrency: It assumes that conflicts are likely between concurrent transactions. This method ensures access to the data but can lead to the degradation of performance
   
• Row versioning: This strategy includes that each row in the database has a version number, and it gets updated when a transaction modifies a row

33. Explain the ways to increase performance of Entity Framework?

Ans: Make use of eager loading, compiled queries, and stay away from the N+1 query problem to improve Entity Framework speed. When performing bulk updates, disable auto-detect changes and use AsNoTracking() for read-only data. Use batch updates for efficiency and stored processes for complex operations; avoid loading unneeded data. Design and index your database properly to maximize it. Reduce the number of lengthy transactions, and think about utilizing AsQueryable() with LINQ-to-Objects.

34. What does the DbSet<TEntity> do in Entity Framework?

Ans: DbSet<TEntity> in Entity Framework acts as a gateway to the database for a specific entity type. It represents a collection of entities that map to a table in the database. You can use DbSet<TEntity> to perform common database operations like adding new records, updating existing ones, and deleting records. 

Additionally, DbSet<TEntity> allows you to run LINQ queries to retrieve data from the database. This means you can filter, sort, and project data directly using C# code, which is then translated into SQL by Entity Framework. DbSet<TEntity> is central to interacting with your data in Entity Framework, providing a strongly-typed, intuitive API for working with entities.

35. What is meant by the SQL injection attack?

Ans: SQL injection is a type of security attack. It inserts malicious SQL code into user inputs or backend databases, which can manipulate the application’s SQL statements and potentially gain unauthorized access. This can lead to data breaches and unauthorized data exposure.

36. How can you create a custom convention in Entity Framework Code First?

Ans:To create a custom convention in Entity Framework Code First, you start by making a class that inherits from the Convention class. In this class, you override the Apply method, where you define your custom rules that will be applied to your model. For example, you might create a convention that automatically adds a specific prefix to all table names or configures a particular data type for all string properties.

After defining your convention, you need to register it in the OnModelCreating method of your DbContext class. This is done by calling modelBuilder.Conventions.Add<MyCustomConvention>(). This ensures that the convention is applied to the entire model when the context is being created. Custom conventions are a powerful way to enforce consistent rules across your model, reducing the need to manually configure each entity and property.

37. What is meant by the Entity SQL?

Ans: Entity SQL is a query language specifically designed for querying the conceptual model within Entity Framework. Unlike traditional SQL, which operates directly on database tables, Entity SQL operates on the conceptual model that represents the data in terms of entities and relationships, abstracted away from the underlying database schema. This allows developers to work at a higher level of abstraction, focusing on the data as it is modeled in the application rather than how it is stored in the database.

Entity SQL is similar to SQL in syntax but is tightly integrated with the Entity Framework's Entity Data Model (EDM). It allows you to perform complex queries, including joins, projections, filtering, and grouping, directly on entities, associations, and complex types defined in the conceptual model. One of the key benefits of Entity SQL is that it supports querying across relationships, enabling you to retrieve related data easily.

38. How do you improve performance when dealing with large data models in Entity Framework?

Ans: To improve performance when working with large data models in Entity Framework, you can use several strategies. First, consider lazy loading, which loads related entities only when they are accessed, reducing the initial load time. Alternatively, eager loading can be used to load all necessary data in one query, reducing the number of database calls. Splitting large models into smaller, more manageable parts can also help, as it reduces the complexity of each query.

Another important technique is to load only the data you need by using projections or selecting specific fields. This minimizes the amount of data transferred from the database. Additionally, using compiled queries for operations that are frequently executed can reduce the overhead of query translation. Finally, managing the lifetime of your DbContext carefully ensures that resources are released promptly, preventing memory leaks and reducing contention for database connections. These practices collectively help in optimizing performance in large-scale applications using Entity Framework.

39. What is the difference between AsNoTracking() and the default tracking in Entity Framework?

Ans: AsNoTracking() lets you run a query without tracking the entities in the DbContext. This improves performance because the context doesn’t need to keep track of changes. By default, Entity Framework tracks changes to entities so you can save updates or deletions later.

40. How can you set a custom naming convention for database tables and columns in Entity Framework?

Ans: To set a custom naming convention for tables and columns in Entity Framework, override the OnModelCreating method in your DbContext. Use the modelBuilder to apply naming rules. For tables, iterate over all entity types and use SetTableName() to add prefixes or suffixes. For columns, loop through each entity’s properties and use SetColumnName() to apply a naming convention, like converting property names to snake_case. A utility method can handle the snake_case conversion. This approach ensures consistent naming across the entire model, making the database schema easier to manage and understand.

MCQ on Entity Framework

1. What does the Include() method do in Entity Framework?

• A) It includes related data in the query results.
• B) It excludes related data from the query results.
• C) It aggregates related data.
• D) It maps data to database tables.
   

Ans: A) It includes related data in the query results.

2. Which approach in Entity Framework lets you define the database schema in C# classes?

• A) Database First
• B) Model First
• C) Code First
• D) Schema First
   

Ans: C) Code First

3. What does the DbContext.SaveChanges() method do in Entity Framework?

• A) It saves the database state.
• B) It commits the changes made in the context to the database.
• C) It refreshes the context with the latest data from the database.
• D) It cancels all pending changes in the context.
   

Ans: B) It commits the changes made in the context to the database.

4. Which of these is NOT a valid inheritance strategy in Entity Framework?

• A) Table-per-Hierarchy (TPH)
• B) Table-per-Concrete Class (TPC)
• C) Table-per-Entity (TPE)
• D) Table-per-Type (TPT)
   

Ans: C) Table-per-Entity (TPE)

5. Which method is used to load related data eagerly in Entity Framework?

• A) Load()
• B) Find()
• C) Include()
• D) Track()
   

Ans: C) Include()

6. How do you prevent SQL injection attacks in Entity Framework?

• A) By using raw SQL queries
• B) By using parameterized queries
• C) By using string concatenation
• D) By using inline SQL
   

Ans: B) By using parameterized queries

7. What is the default behavior for cascading in Entity Framework?

• A) No action
• B) Cascade
• C) Set null
• D) Restrict
   

Ans: B) Cascade

8. Which method is used to load related data after the initial query in Entity Framework?

• A) LoadRelated()
• B) LoadInclude()
• C) IncludeRelated()
• D) Load()
   

Ans: D) Load()

9. Which feature in Entity Framework allows you to run raw SQL queries?

• A) ExecuteQuery()
• B) ExecuteRawSQL()
• C) FromSql()
• D) RawQuery()
   

Ans: C) FromSql()

10. What is the main benefit of using the Lazy Loading feature in Entity Framework?

• A) It loads all related data in advance.
• B) It saves memory by loading related data only when needed.
• C) It improves query performance by including related data in the initial query.
• D) It automatically tracks changes to related data.
   

Ans: B) It saves memory by loading related data only when needed.

Frequently Asked Questions

Which approach is best for Entity Framework?

The best approach for Entity Framework depends on the project requirements. Some prefer Database-First for working with legacy databases, while others prefer Code-First for more control over the database schema. Model-First can be a good option for visualizing and designing the data model.

What are the 3 approaches in Entity Framework?

There are three approaches to Entity Framework: 

• Database-First starts with an existing database.
• Model-First starts with the conceptual model of the data.
• Code-First starts with the code and develops the database schema.

In which scenarios can we use Entity Framework?

Entity Framework can be used in scenarios where .NET applications need to interact with a database. It is used for creating, reading, updating, and deleting data, mapping between data tables and object-oriented entities, and managing database-related operations.

What are some arguments against Entity Framework?

Arguments against Entity Framework contain problems over performance and generated SQL code, difficulty working with complex database structures, and limitations in certain scenarios, such as working with NoSQL databases.

Conclusion

This article provides an in-depth discussion on basic, intermediate, and advanced Entity Framework interview questions. We hope that this blog has helped you enhance your knowledge about the Entity framework Interview questions and if you would like to learn more, check out our articles ASP.NET and .NET Framework.