31 Advanced Entity Framework Core Interview Questions and Answers (2025)

Blog / 31 Advanced Entity Framework Core Interview Questions and Answers (2025)

Entity Framework Core bridges your C# domain models to SQL with fluent LINQ, change tracking, and migrations that evolve schemas on command.

Knowing how queries translate to SQL, how tracking scopes affect performance, and when to bypass the context separates architects from “just-CRUD” coders.

Q1.

What is Entity Framework Core?

Junior

Entity Framework Core is an open-source, lightweight, and cross-platform ORM framework for .NET.
It allows developers to interact with databases using .NET objects, abstracting away the underlying database interactions and reducing the need to write raw SQL queries.

Q2.

How does Entity Framework Core simplify data access in .NET?

Junior

EF Core simplifies data access by mapping .NET classes to database tables, allowing developers to perform database operations using LINQ (Language Integrated Query) against these objects.
It automates tasks such as generating SQL queries, managing database connections, and mapping results back to .NET objects. This reduces the amount of code developers need to write and makes the code more maintainable.

Q3.

What are the key components of Entity Framework Core?

Junior

The key components of EF Core include:

DbContext, which represents a session with the database and acts as a gateway for performing CRUD operations.
DbSet, which represents a collection of entities of a particular type; and Entities, which are the .NET classes that map to database tables.
LINQ to Entities is another crucial component that allows querying entities using LINQ syntax.

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Q4.

What is the difference between Entity Framework Core and ADO.NET?

Junior

ADO.NET is a lower-level data access technology in .NET that requires developers to write explicit SQL queries and manage database connections directly.
EF Core provides a higher level of abstraction, automating many of these tasks and allowing developers to work with data as objects. While ADO.NET offers more control, EF Core simplifies development and reduces boilerplate code.

Q5.

Can you explain the concept of DbContext in Entity Framework Core?

Junior

The DbContext class in EF Core represents a connection to the database and acts as a container for entities.
It is responsible for managing entity objects during runtime, including tracking changes, performing queries, and saving data to the database.
It serves as the central hub for all database interactions within an application.

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Q6.

What are Entities in Entity Framework Core?

Junior

Entities in EF Core are plain old CLR objects (POCOs) that represent the data in the database.
Each entity class typically maps to a table in the database, and its properties map to the columns of that table.
These classes do not need to inherit from any EF Core-specific base class, keeping them clean and focused on the data they represent.

Q7.

Which approach (Code-First, Database-First, Model-First) is generally considered the best?

Junior

There is no universally "best" approach; the choice depends on the specific project requirements and the existing infrastructure.
Code-First is often preferred for new applications where developers have full control over the domain model and want to follow a domain-driven design approach.
Database-First is suitable when working with existing databases.
Model-First is less commonly used in modern development workflows.

Q8.

What is meant by migration in Entity Framework Core?

Junior

Migrations in EF Core provide a way to manage changes to the database schema over time.
When the entity model changes, developers create migrations that describe the necessary database modifications.
These migrations can then be applied to the database to update the schema without losing existing data.
This ensures that the database schema stays in sync with the application's data model.

Q9.

What is the purpose of the DbContext.SaveChanges() method?

Junior

The SaveChanges() method in EF Core is responsible for persisting all the changes made to the tracked entities within the DbContext to the underlying database.
This includes inserting new entities, updating existing ones, and deleting entities that have been marked for removal.
All these changes are typically performed within a transaction.

Q10.

What are the different Entity States in Entity Framework Core?

Junior

Entities in EF Core can be in one of the following states:

Added: The entity has been added to the context but not yet saved to the database.
Modified: The entity has been retrieved from the database and has been modified.
Deleted: The entity has been marked for deletion from the database.
Unchanged: The entity has been retrieved from the database and has not been modified.
Detached: The entity is not being tracked by the DbContext.

Q11.

What is Lazy Loading in Entity Framework Core, and what are its pros and cons?

Mid

Lazy loading is a feature where related entities are loaded from the database only when they are accessed for the first time through a navigation property.
The primary advantage is that it reduces the initial load time and memory usage by only fetching the necessary data.
However, a significant drawback is the potential for the N+1 query problem, where accessing related entities for a list of primary entities can result in numerous additional database queries, leading to performance issues if not managed carefully.

Q12.

What is Eager Loading in Entity Framework Core, and when would you use it?

Mid

Eager loading is a technique where related entities are loaded along with the main entity in a single query using the Include() method.
This avoids the N+1 query problem associated with lazy loading and is beneficial when you know you will need the related data upfront.
By fetching all necessary data in one go, it can improve the efficiency of data access operations.

Q13.

What is Explicit Loading in Entity Framework Core?

Mid

Explicit loading involves manually loading related entities at a later point in time, after the primary entity has been retrieved.
This can be achieved using methods like Collection(e => e.RelatedEntities).Load() for collections or Reference(e => e.RelatedEntity).Load() for single references on the DbContext.Entry(entity) object.
It provides more control over when and what related data is loaded.

Q14.

What is the difference between Include() and ThenInclude()?

Mid

Include() is used to load the first level of related entities.
ThenInclude() is used to load further levels of related entities in a navigation property that is part of an already included entity.
For example, if you have Order -> OrderDetails -> Product, you would use Include(o => o.OrderDetails).ThenInclude(od => od.Product) to eagerly load the product information for each order detail of each order.

Q15.

What is the purpose of the AsNoTracking() method in Entity Framework Core, and when should you use it?

Mid

The AsNoTracking() method is used to query entities without keeping track of their state in the DbContext's change tracker.
This improves performance, especially for read-only queries, as EF Core does not need to spend resources on tracking changes.
It should be used when you retrieve data only for display or processing and do not intend to update the retrieved entities within the same DbContext scope.

Q16.

How can you filter data using Entity Framework Core?

Mid

Data filtering in EF Core is primarily done using the Where() clause in LINQ queries.
This allows developers to specify conditions that entities must meet to be included in the query results.
The conditions can involve properties of the entity and can be combined using logical operators.

Q17.

How do you order data using Entity Framework Core?

Mid

Ordering of data in EF Core is achieved using the OrderBy() method for ascending order and the OrderByDescending() method for descending order in LINQ queries.
These methods take a lambda expression specifying the property to order by.

Q18.

What are the different types of inheritance supported by Entity Framework Core?

Mid

EF Core supports three main types of inheritance mapping:

Table-per-Hierarchy (TPH): Where all types in an inheritance hierarchy are mapped to a single database table with a discriminator column;
Table-per-Type (TPT): Where each type in the hierarchy is mapped to its own table, with a table for the base type and separate tables for each derived type.
Table-per-Concrete-Type (TPC): Where each concrete type in the hierarchy is mapped to its own table, and common properties are repeated in each table.

Q19.

How do you create a new migration in Entity Framework Core?

Mid

A new migration in EF Core is created using the Add-Migration command in the Package Manager Console within Visual Studio or by using the dotnet ef migrations add <MigrationName> command in the .NET CLI.
This command generates a C# code file that defines the database schema changes required to match the current state of the entity model.

Q20.

What is the role of the OnModelCreating method in DbContext?

Mid

The OnModelCreating method is a virtual method in the DbContext class that is called when the model is being created.
It provides a place to configure the model using the Fluent API, allowing developers to define table mappings, relationships, constraints, and other model-specific configurations that cannot be easily expressed using data annotations alone.

Q21.

What are Data Annotations and Fluent API in Entity Framework Core?

Mid

Both Data Annotations and Fluent API are used to configure how EF Core maps entities to the database schema and defines relationships.

Data Annotations are attributes that can be applied directly to the entity classes and their properties to specify configurations like primary keys, foreign keys, and validation rules.
Fluent API provides a more powerful and flexible way to configure the model within the OnModelCreating method of the DbContext. It allows for more complex configurations and can override configurations specified by data annotations.

Q22.

What is Deferred Execution in the context of LINQ queries in Entity Framework Core?

Mid

Deferred execution means that LINQ queries in EF Core are not executed immediately when they are defined.
Instead, the query is only executed when the results are actually needed, such as when the code iterates over the results (e.g., using a foreach loop) or when a method that forces execution is called (like ToList(), FirstOrDefault(), etc.).
This behavior allows for further modification of the query before it hits the database, which can be beneficial for performance but also requires understanding when the query will actually be executed to avoid unexpected behavior or performance issues.

Q23.

How can you improve the performance of Entity Framework Core in an application?

Senior

Performance optimization in EF Core involves several strategies.

Using AsNoTracking() for read-only queries reduces tracking overhead.
Employing eager loading with Include() judiciously can prevent the N+1 query problem.
Projections using Select() to retrieve only necessary data can minimize data transfer.
Compiled queries can improve performance for frequently executed queries.
Ensuring proper database indexing is crucial for query speed.
Utilizing asynchronous operations (ToListAsync(), etc.) enhances scalability.
Batch updates and deletes can be more efficient for bulk operations.
It is important to consider the trade-offs between these techniques, as some might fetch more data than needed in certain scenarios.

Q24.

Explain the N+1 query problem in Entity Framework Core and how to avoid it.

Senior

The N+1 query problem occurs when an application executes one query to retrieve a list of primary entities, and then for each of these entities, it executes an additional query to load related data (e.g., through lazy loading).
This results in N+1 database calls, where N is the number of primary entities, which can severely impact performance.
The primary way to avoid this is by using eager loading with the Include() method to fetch all necessary related data in a single query.

Q25.

What are compiled queries in Entity Framework Core, and when would you use them?

Senior

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Q26.

How does Entity Framework Core handle concurrency?

Senior

Q27.

How do you use Stored Procedures with Entity Framework Core?

Senior

Q28.

What is the EF Core change tracker, and how does it work?

Senior

Q29.

What is the purpose of the Model Snapshot in EF Core migrations?

Senior

Q30.

When would you consider using raw SQL queries in Entity Framework Core instead of LINQ?

Senior

Q31.

What are shadow properties in Entity Framework Core?

Senior

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