Interview Q&A

Answer: Entity Framework Core (EF Core) is a modern, lightweight, cross-platform, open-source ORM (Object-Relational Mapper) for .NET. It allows developers to interact with databases using C# objects rather than SQL queries.

What interviewers expect

• A clear definition tied to EF Core in Entity Framework Core projects
• Trade-offs (performance, maintainability, security, cost)
• When you would and would not use it in production

Real-world example

In a production Entity Framework Core application, teams apply this when handling user-facing features or integration boundaries. For example, you might use it during a sprint where reliability and observability matter—logging metrics, validating edge cases, and documenting the decision in an ADR so future developers understand why the approach was chosen.

How to explain in the interview

1. Define the concept in one or two sentences.
2. Context — where it fits in Entity Framework Core architecture.
3. Example — a specific project, bug, or performance win.
4. Trade-off — what you gain vs what you sacrifice.

Tip: Practice aloud on Toolliyo mock interview or the Interview Q&A section before your real interview.

Answer: ORM is a technique that maps objects in code to relational database tables. EF Core implements ORM by mapping .NET classes (entities) to database tables using DbContext, DbSet, and conventions or Fluent API.

What interviewers expect

• A clear definition tied to EF Core in Entity Framework Core projects
• Trade-offs (performance, maintainability, security, cost)
• When you would and would not use it in production

Real-world example

In a production Entity Framework Core application, teams apply this when handling user-facing features or integration boundaries. For example, you might use it during a sprint where reliability and observability matter—logging metrics, validating edge cases, and documenting the decision in an ADR so future developers understand why the approach was chosen.

How to explain in the interview

1. Define the concept in one or two sentences.
2. Context — where it fits in Entity Framework Core architecture.
3. Example — a specific project, bug, or performance win.
4. Trade-off — what you gain vs what you sacrifice.

Tip: Practice aloud on Toolliyo mock interview or the Interview Q&A section before your real interview.

Answer: How does EF Core implement it? ORM is a technique that maps objects in code to relational database tables. EF Core implements ORM by mapping .NET classes (entities) to database tables using DbContext, DbSet, and conventions or Fluent API.

What interviewers expect

• A clear definition tied to EF Core in Entity Framework Core projects
• Trade-offs (performance, maintainability, security, cost)
• When you would and would not use it in production

Real-world example

In a production Entity Framework Core application, teams apply this when handling user-facing features or integration boundaries. For example, you might use it during a sprint where reliability and observability matter—logging metrics, validating edge cases, and documenting the decision in an ADR so future developers understand why the approach was chosen.

How to explain in the interview

1. Define the concept in one or two sentences.
2. Context — where it fits in Entity Framework Core architecture.
3. Example — a specific project, bug, or performance win.
4. Trade-off — what you gain vs what you sacrifice.

Tip: Practice aloud on Toolliyo mock interview or the Interview Q&A section before your real interview.

Answer: DbContext is the primary class for interacting with the database in EF Core. It: Manages database connections Tracks changes to entities Provides methods for querying and saving data Configures models and relationships

What interviewers expect

• A clear definition tied to EF Core in Entity Framework Core projects
• Trade-offs (performance, maintainability, security, cost)
• When you would and would not use it in production

Real-world example

In a production Entity Framework Core application, teams apply this when handling user-facing features or integration boundaries. For example, you might use it during a sprint where reliability and observability matter—logging metrics, validating edge cases, and documenting the decision in an ADR so future developers understand why the approach was chosen.

How to explain in the interview

1. Define the concept in one or two sentences.
2. Context — where it fits in Entity Framework Core architecture.
3. Example — a specific project, bug, or performance win.
4. Trade-off — what you gain vs what you sacrifice.

Tip: Practice aloud on Toolliyo mock interview or the Interview Q&A section before your real interview.

What responsibilities does it have?

DbContext is the primary class for interacting with the database in EF Core. It:

• Manages database connections
• Tracks changes to entities
• Provides methods for querying and saving data
• Configures models and relationships

Answer: DbSet<T> represents a collection of entities of type T in the context. Each DbSet maps to a table in the database, where T is the type of the entity.

What interviewers expect

• A clear definition tied to EF Core in Entity Framework Core projects
• Trade-offs (performance, maintainability, security, cost)
• When you would and would not use it in production

Real-world example

In a production Entity Framework Core application, teams apply this when handling user-facing features or integration boundaries. For example, you might use it during a sprint where reliability and observability matter—logging metrics, validating edge cases, and documenting the decision in an ADR so future developers understand why the approach was chosen.

How to explain in the interview

1. Define the concept in one or two sentences.
2. Context — where it fits in Entity Framework Core architecture.
3. Example — a specific project, bug, or performance win.
4. Trade-off — what you gain vs what you sacrifice.

Tip: Practice aloud on Toolliyo mock interview or the Interview Q&A section before your real interview.

Answer: How does it map to database tables? DbSet<T> represents a collection of entities of type T in the context. Each DbSet maps to a table in the database, where T is the type of the entity.

What interviewers expect

• A clear definition tied to EF Core in Entity Framework Core projects
• Trade-offs (performance, maintainability, security, cost)
• When you would and would not use it in production

Real-world example

In a production Entity Framework Core application, teams apply this when handling user-facing features or integration boundaries. For example, you might use it during a sprint where reliability and observability matter—logging metrics, validating edge cases, and documenting the decision in an ADR so future developers understand why the approach was chosen.

How to explain in the interview

1. Define the concept in one or two sentences.
2. Context — where it fits in Entity Framework Core architecture.
3. Example — a specific project, bug, or performance win.
4. Trade-off — what you gain vs what you sacrifice.

Tip: Practice aloud on Toolliyo mock interview or the Interview Q&A section before your real interview.

Answer: POCO (Plain Old CLR Object) is a simple class without any dependency on EF Core or any base class. EF Core uses POCOs as entities for data modeling.

What interviewers expect

• A clear definition tied to EF Core in Entity Framework Core projects
• Trade-offs (performance, maintainability, security, cost)
• When you would and would not use it in production

Real-world example

In a production Entity Framework Core application, teams apply this when handling user-facing features or integration boundaries. For example, you might use it during a sprint where reliability and observability matter—logging metrics, validating edge cases, and documenting the decision in an ADR so future developers understand why the approach was chosen.

How to explain in the interview

1. Define the concept in one or two sentences.
2. Context — where it fits in Entity Framework Core architecture.
3. Example — a specific project, bug, or performance win.
4. Trade-off — what you gain vs what you sacrifice.

Tip: Practice aloud on Toolliyo mock interview or the Interview Q&A section before your real interview.

Navigation properties allow navigation from one entity to related entities. They define

relationships (one-to-one, one-to-many, many-to-many).

Example:

public class Order
{
public int Id { get; set; }
public Customer Customer { get; set; } // Navigation property
}

Answer: LINQ (Language Integrated Query) lets you query collections using C# syntax. LINQ to Entities is LINQ querying against the EF Core model, translated to SQL and executed in the database.

What interviewers expect

• A clear definition tied to EF Core in Entity Framework Core projects
• Trade-offs (performance, maintainability, security, cost)
• When you would and would not use it in production

Real-world example

In a production Entity Framework Core application, teams apply this when handling user-facing features or integration boundaries. For example, you might use it during a sprint where reliability and observability matter—logging metrics, validating edge cases, and documenting the decision in an ADR so future developers understand why the approach was chosen.

How to explain in the interview

1. Define the concept in one or two sentences.
2. Context — where it fits in Entity Framework Core architecture.
3. Example — a specific project, bug, or performance win.
4. Trade-off — what you gain vs what you sacrifice.

Tip: Practice aloud on Toolliyo mock interview or the Interview Q&A section before your real interview.

Answer: What is “LINQ to Entities”? LINQ (Language Integrated Query) lets you query collections using C# syntax. LINQ to Entities is LINQ querying against the EF Core model, translated to SQL and executed in the database.

What interviewers expect

• A clear definition tied to EF Core in Entity Framework Core projects
• Trade-offs (performance, maintainability, security, cost)
• When you would and would not use it in production

Real-world example

In a production Entity Framework Core application, teams apply this when handling user-facing features or integration boundaries. For example, you might use it during a sprint where reliability and observability matter—logging metrics, validating edge cases, and documenting the decision in an ADR so future developers understand why the approach was chosen.

How to explain in the interview

1. Define the concept in one or two sentences.
2. Context — where it fits in Entity Framework Core architecture.
3. Example — a specific project, bug, or performance win.
4. Trade-off — what you gain vs what you sacrifice.

Tip: Practice aloud on Toolliyo mock interview or the Interview Q&A section before your real interview.

// Create

context.Users.Add(new User { Name = "John" });

context.SaveChanges();

// Read

var user = context.Users.FirstOrDefault(u => u.Id == 1);

// Update

user.Name = "Jane";

context.SaveChanges();

// Delete

context.Users.Remove(user);

context.SaveChanges();

Code First is an EF Core approach where you define your database schema using C#

classes, and EF Core generates the database from your code.

✅ Advantages:

• Full control via C# code (POCOs)
• Easily version-controlled
• Supports migrations to handle schema evolution
• Works well with Domain-Driven Design

📌 When to use:

When you're starting a new project or prefer designing schema in code.

Advantages and when to use it

Code First is an EF Core approach where you define your database schema using C#

classes, and EF Core generates the database from your code.

✅ Advantages:

• Full control via C# code (POCOs)
• Easily version-controlled
• Supports migrations to handle schema evolution
• Works well with Domain-Driven Design

📌 When to use:

When you're starting a new project or prefer designing schema in code.

Database First involves generating C# entity classes and a DbContext from an existing

database.

✅ Pros:

• Quick start if the DB already exists
• Ensures model aligns with legacy databases

❌ Cons:

• Harder to version control
• Schema changes must be manually re-scaffolded

📌 When to use:

For integrating with existing databases or legacy systems.

Use‑cases and pros and cons

Database First involves generating C# entity classes and a DbContext from an existing

database.

✅ Pros:

• Quick start if the DB already exists
• Ensures model aligns with legacy databases

❌ Cons:

• Harder to version control
• Schema changes must be manually re-scaffolded

📌 When to use:

For integrating with existing databases or legacy systems.

Answer: Model First allows creating a database model using a designer (EDMX file), then generating both the database and code from that model. ⚠ EF Core does not support Model First. This approach was available in EF6 with Visual Studio tooling.

What interviewers expect

• A clear definition tied to EF Core in Entity Framework Core projects
• Trade-offs (performance, maintainability, security, cost)
• When you would and would not use it in production

Real-world example

In a production Entity Framework Core application, teams apply this when handling user-facing features or integration boundaries. For example, you might use it during a sprint where reliability and observability matter—logging metrics, validating edge cases, and documenting the decision in an ADR so future developers understand why the approach was chosen.

How to explain in the interview

1. Define the concept in one or two sentences.
2. Context — where it fits in Entity Framework Core architecture.
3. Example — a specific project, bug, or performance win.
4. Trade-off — what you gain vs what you sacrifice.

Tip: Practice aloud on Toolliyo mock interview or the Interview Q&A section before your real interview.

Is it used in EF Core?

Model First allows creating a database model using a designer (EDMX file), then generating

both the database and code from that model.

⚠ EF Core does not support Model First. This approach was available in EF6 with Visual

Studio tooling.

• A migration snapshot is a C# file (e.g., ModelSnapshot.cs) automatically created

by EF Core.

• It represents the current model state.
• EF uses it to compare changes in future migrations.
• Located in the Migrations folder, named like

[YourDbContext]ModelSnapshot.cs.

Answer: fter they are loaded from the database. This allows EF Core to generate the correct SQL INSERT, UPDATE, or DELETE statements when SaveChanges() is called.

What interviewers expect

• A clear definition tied to EF Core in Entity Framework Core projects
• Trade-offs (performance, maintainability, security, cost)
• When you would and would not use it in production

Real-world example

In a production Entity Framework Core application, teams apply this when handling user-facing features or integration boundaries. For example, you might use it during a sprint where reliability and observability matter—logging metrics, validating edge cases, and documenting the decision in an ADR so future developers understand why the approach was chosen.

How to explain in the interview

1. Define the concept in one or two sentences.
2. Context — where it fits in Entity Framework Core architecture.
3. Example — a specific project, bug, or performance win.
4. Trade-off — what you gain vs what you sacrifice.

Tip: Practice aloud on Toolliyo mock interview or the Interview Q&A section before your real interview.

Change tracking is the process by which EF Core keeps track of changes made to entities

after they are loaded from the database. This allows EF Core to generate the correct SQL

INSERT, UPDATE, or DELETE statements when SaveChanges() is called.

re monitored and persisted.

• Untracked queries: EF does not monitor the returned entities. Faster, read-only

ccess.

Tracked (default):

var user = context.Users.FirstOrDefault();

Untracked:

var user = context.Users.AsNoTracking().FirstOrDefault();

• Tracked queries: EF Core tracks entities returned from the query. Changes to them

are monitored and persisted.

• Untracked queries: EF does not monitor the returned entities. Faster, read-only

access.

Tracked (default):

var user = context.Users.FirstOrDefault();

Untracked:

var user = context.Users.AsNoTracking().FirstOrDefault();

.AsNoTracking() tells EF Core not to track entities in the returned query.

✅ Use when:

• Read-only operations
• Improving performance for large queries
• Preventing memory overhead of tracking

Example:

var users = context.Users.AsNoTracking().ToList();

When to use it?

.AsNoTracking() tells EF Core not to track entities in the returned query.

✅ Use when:

• Read-only operations
• Improving performance for large queries
• Preventing memory overhead of tracking

Example:

var users = context.Users.AsNoTracking().ToList();