Top 25 Entity Framework Core Interview Questions and Answers for Beginners
Introduction
Entity Framework Core (EF Core) is a lightweight, extensible, and cross-platform version of Microsoft’s popular Entity Framework data access technology. As an Object-Relational Mapper (ORM), EF Core simplifies database interactions by allowing developers to work with databases using .NET objects.
For beginners preparing for technical interviews, understanding EF Core is essential, especially for roles involving .NET development. This guide covers the top 25 Entity Framework Core interview questions and answers, structured to help beginners grasp fundamental concepts, best practices, and common pitfalls.
Whether you're a student, a junior developer, or transitioning into .NET, this comprehensive guide will strengthen your EF Core knowledge and boost your confidence in technical interviews.
1. What Is Entity Framework Core?
Answer:
Entity Framework Core (EF Core) is an open-source, lightweight, and cross-platform ORM framework developed by Microsoft. It enables .NET developers to interact with databases using .NET objects, eliminating the need for most of the data-access code.
Key Features:
Supports multiple database providers (SQL Server, SQLite, PostgreSQL, MySQL, etc.).
Works with .NET Core and .NET 5+.
Provides LINQ-based querying.
Supports migrations for database schema updates.
Lightweight and extensible compared to Entity Framework 6.
2. What Are the Key Differences Between EF Core and EF 6?
Answer:
EF Core is the future of Microsoft’s ORM, while EF 6 remains in maintenance mode.
3. What Are the Different Approaches to Database Modeling in EF Core?
Answer:
EF Core supports three primary approaches:
Code-First:
Define entity classes and DbContext first.
EF Core generates the database schema.
Best for new projects where the database doesn’t exist.
Database-First:
Reverse-engineer an existing database into entity classes.
Uses Scaffold-DbContext command.
Useful when working with legacy databases.
Model-First (Less Common in EF Core):
Design a model in the EF Designer, then generate SQL.
More common in EF 6 than EF Core.
4. Explain DbContext in EF Core
Answer:
DbContext is a central class in EF Core that represents a session with the database. It is responsible for:
Managing database connections.
Tracking changes to entities.
Executing queries and saving data.
Handling transactions.
Example:
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public class AppDbContext : DbContext
{
public DbSet<Product> Products { get; set; }
protected override void OnConfiguring(DbContextOptionsBuilder options)
=> options.UseSqlServer("Server=.;Database=ShopDb;Trusted_Connection=True;");
}
5. What Are Entity Framework Core Migrations?
Answer:
Migrations allow developers to update the database schema incrementally as the data model evolves.
Key Commands:
Add-Migration <Name> – Creates a new migration.
Update-Database – Applies pending migrations.
Remove-Migration – Removes the last migration.
Example:
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dotnet ef migrations add InitialCreate
dotnet ef database update
6. How Does EF Core Handle Relationships?
Answer:
EF Core supports three types of relationships:
One-to-One:
One entity relates to exactly one other entity.
Example: User ↔ UserProfile.
One-to-Many:
One entity relates to multiple entities.
Example: Blog ↔ Posts.
Many-to-Many:
Requires a join entity (junction table).
Example: Student ↔ Course (via StudentCourse).
Configuration Example:
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modelBuilder.Entity<Blog>()
.HasMany(b => b.Posts)
.WithOne(p => p.Blog)
.HasForeignKey(p => p.BlogId);
7. What Is Lazy Loading in EF Core?
Answer:
Lazy Loading delays the loading of related entities until they are accessed.
How to Enable:
Install Microsoft.EntityFrameworkCore.Proxies.
Use UseLazyLoadingProxies() in OnConfiguring.
Pros & Cons:
✔ Reduces initial query load.
✖ May cause N+1 query issues.
8. What Is Eager Loading in EF Core?
Answer:
Eager Loading loads related data in a single query using .Include().
Example:
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var blogs = context.Blogs
.Include(b => b.Posts)
.ToList();
Best For:
When you know related data is needed upfront.
9. What Is Explicit Loading in EF Core?
Answer:
Explicit Loading loads related data on-demand using .Load().
Example:
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var blog = context.Blogs.Find(1);
context.Entry(blog)
.Collection(b => b.Posts)
.Load();
Use Case:
When related data is needed conditionally.
10. How Do You Execute Raw SQL in EF Core?
Answer:
Use FromSqlRaw or ExecuteSqlRaw.
Example:
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var products = context.Products
.FromSqlRaw("SELECT * FROM Products WHERE Price > {0}", 50)
.ToList();
For Non-Query Commands:
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context.Database.ExecuteSqlRaw("DELETE FROM Products WHERE IsExpired = 1");
11. What Is Change Tracking in EF Core?
Answer:
Change Tracking monitors modifications to entities so EF Core knows what to update in the database.
Modes:
Snapshot Change Tracking (Default): Compares original and current values.
Change Tracking Proxies: Uses runtime proxies for automatic detection.
Disabling Change Tracking:
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context.ChangeTracker.QueryTrackingBehavior = QueryTrackingBehavior.NoTracking;
12. How Do You Optimize EF Core Performance?
Answer:
Use AsNoTracking() for read-only queries.
Batch operations (e.g., AddRange).
Avoid N+1 queries (use .Include or explicit joins).
Use compiled queries (EF.CompileAsyncQuery).
Index frequently queried columns.
13. What Is the Difference Between IQueryable and IEnumerable in EF Core?
Answer:
Example:
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IQueryable<Product> query = db.Products.Where(p => p.Price > 100); // DB Query
IEnumerable<Product> list = query.ToList(); // Executes SQL
14. How Do You Handle Transactions in EF Core?
Answer:
1. Automatic Transactions:
EF Core wraps SaveChanges() in a transaction.
2. Manual Transactions:
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using (var transaction = context.Database.BeginTransaction())
{
try
{
context.Products.Add(product);
context.SaveChanges();
transaction.Commit();
}
catch
{
transaction.Rollback();
}
}
15. What Are Shadow Properties in EF Core?
Answer:
Shadow Properties are properties not defined in the entity class but exist in the database.
Example:
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modelBuilder.Entity<Blog>()
.Property<DateTime>("LastUpdated");
Use Cases:
Audit fields (CreatedDate, ModifiedBy).
16. How Do You Seed Data in EF Core?
Answer:
Use HasData in OnModelCreating.
Example:
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modelBuilder.Entity<Blog>().HasData(
new Blog { Id = 1, Name = "EF Core Blog" }
);
For Migrations:
Add seed data in the Up() method.
17. What Is a DbSet in EF Core?
Answer:
A DbSet<T> represents a collection of entities in the context.
Example:
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public class AppDbContext : DbContext
{
public DbSet<Product> Products { get; set; }
}
Key Methods:
Add(), Remove(), Find(), Where().
18. How Do You Handle Concurrency Conflicts in EF Core?
Answer:
Use Concurrency Tokens (e.g., [Timestamp] or IsConcurrencyToken()).
Example:
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modelBuilder.Entity<Product>()
.Property(p => p.RowVersion)
.IsRowVersion();
Handling Conflicts:
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try
{
await context.SaveChangesAsync();
}
catch (DbUpdateConcurrencyException ex)
{
// Resolve conflict
}
19. What Are Global Query Filters in EF Core?
Answer:
Global Query Filters apply conditions to all queries for an entity.
Example (Soft Delete):
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modelBuilder.Entity<Product>()
.HasQueryFilter(p => !p.IsDeleted);
Disabling Filters:
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context.Products.IgnoreQueryFilters().ToList();
20. How Do You Log EF Core Queries?
Answer:
Use LogTo or Microsoft.Extensions.Logging.
Example:
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optionsBuilder.UseSqlServer(connectionString)
.LogTo(Console.WriteLine, LogLevel.Information);
Best For:
Debugging performance issues.
21. What Is the Difference Between First() and FirstOrDefault()?
Answer:
Example:
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var product = context.Products.First(p => p.Id == 1); // Throws if missing
var product = context.Products.FirstOrDefault(p => p.Id == 1); // Returns null
22. How Do You Implement Soft Delete in EF Core?
Answer:
Add an IsDeleted property.
Apply a global query filter.
Override SaveChanges to handle deletion.
Example:
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modelBuilder.Entity<Product>()
.HasQueryFilter(p => !p.IsDeleted);
public override int SaveChanges()
{
foreach (var entry in ChangeTracker.Entries())
{
if (entry.State == EntityState.Deleted)
{
entry.State = EntityState.Modified;
entry.CurrentValues["IsDeleted"] = true;
}
}
return base.SaveChanges();
}
23. What Are Navigation Properties in EF Core?
Answer:
Navigation properties define relationships between entities.
Example:
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public class Blog
{
public int Id { get; set; }
public ICollection<Post> Posts { get; set; } // Navigation property
}
Types:
Reference Navigation (e.g., Blog → User).
Collection Navigation (e.g., Blog → Posts).
24. How Do You Update a Database Using Migrations?
Answer:
Modify entity classes.
Run Add-Migration <Name>.
Run Update-Database.
Rollback:
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dotnet ef database update PreviousMigration
25. What Are the Best Practices for Using EF Core?
Answer:
✔ Use async/await for scalability.
✔ Avoid SELECT * (project only needed columns).
✔ Use indexes for frequently queried fields.
✔ Dispose DbContext properly (using block).
✔ Monitor SQL queries for performance.
FAQs
1. Is EF Core better than Dapper?
EF Core is better for rapid development, while Dapper is faster for raw SQL.
2. Can EF Core work with NoSQL databases?
Yes, via providers like Cosmos DB.
3. How do you handle database schema changes?
Use Migrations (Add-Migration + Update-Database).
4. What is the difference between Find() and FirstOrDefault()?
Find() checks the local cache first; FirstOrDefault() always queries the database.
5. How do you execute a stored procedure in EF Core?
Use FromSqlRaw or ExecuteSqlRaw.
6. Can EF Core be used in .NET Framework?
Yes, but it’s primarily designed for .NET Core/.NET 5+.
7. How do you configure a one-to-one relationship?
Use HasOne().WithOne().
8. What is the purpose of OnModelCreating?
To configure entity relationships, keys, and constraints.
9. How do you disable change tracking for a query?
Use .AsNoTracking().
10. What is a DbContext pool?
A performance optimization that recycles DbContext instances.
Conclusion
Entity Framework Core is a powerful ORM for .NET developers, simplifying database interactions while offering flexibility and performance optimizations. This guide covered the top 25 EF Core interview questions, from basic concepts like DbContext and migrations to advanced topics like concurrency control and performance tuning.
By mastering these concepts, beginners can confidently tackle EF Core-related interview questions and apply best practices in real-world applications.
Next Steps:
Practice building a small EF Core application.
Explore advanced features like owned entities and table splitting.
Stay updated with the latest EF Core releases.
Happy coding! 🚀