Entity Framework Core (EF Core) is the official data access technology provided by Microsoft for .NET applications. It is a modern, lightweight, flexible, and cross-platform Object-Relational Mapper (ORM) that maps C# classes to relational database tables.
EF Core acts as an intelligent middle layer between your application and the database.
Instead of writing SQL manually, developers work with objects, and EF Core automatically:
Builds the database structure
Creates tables and relationships
Generates SQL commands
Tracks changes applied to objects
Updates the database efficiently
This makes EF Core one of the most important technologies for backend systems, enterprise applications, layered architecture, clean architecture, and cloud-native solutions.
This article provides an Entity Framework Core explanation, so the focus remains entirely on EF Core as a framework.
What Is Entity Framework Core?
Entity Framework Core is a data-access framework that handles communication between:
C# Object Models (Entities)
Relational Databases (SQL Server, MySQL, PostgreSQL, Oracle, SQLite)
It allows developers to interact with the database using C# classes, and EF Core automatically generates SQL queries and maps results back.
EF Core is not just a simple ORM—it is:
Cross-platform
Lightweight compared to classic EF
Extensible and modular
Optimized for performance
Suitable for microservices, web APIs, and enterprise apps
How EF Core Works Internally
EF Core's internal working can be broken into several important stages:
1. Model Building
EF Core reads your entity classes and constructs an internal representation (the "model") defining:
Tables
Columns
Keys
Relationships
Constraints
Indexes
Table mappings
This model serves as the blueprint for the database.
2. Database Provider Integration
EF Core supports multiple databases through providers.
The provider decides how SQL should be generated and executed.
Examples:
Microsoft.EntityFrameworkCore.SqlServer
Microsoft.EntityFrameworkCore.Sqlite
Npgsql.EntityFrameworkCore.PostgreSQL
Pomelo.EntityFrameworkCore.MySql
Each provider is responsible for:
SQL translation
Schema metadata
Data type mapping
Query execution
3. Change Tracking
When entities are loaded and modified, EF Core maintains their state:
Added
Modified
Deleted
Unchanged
Detached
EF Core compares the original values with the new values to determine what to update.
Change tracking allows EF Core to generate precise SQL instead of updating entire rows unnecessarily.
4. Saving Changes
When SaveChanges or SaveChangesAsync is called:
EF Core scans all tracked entities
Determines changes
Generates SQL commands
Executes them in the correct order
It automatically handles:
5. Materialization
Materialization is the process of converting raw database results into C# objects.
EF Core has sophisticated algorithms to:
Map columns to object properties
Resolve relationships
Populate navigation properties (if enabled)
Reuse tracked objects when possible
EF Core ensures objects are structured exactly as defined in your domain model.
Key Building Blocks of EF Core
EF Core includes several powerful core components.
1. Entities
An entity is a simple C# class representing a table row.
EF Core uses:
Entities are plain objects, making them simple to work with, test, and maintain.
2. DbContext
DbContext is the central class of EF Core, acting as:
It contains:
DbSet properties
Methods like Add, Remove, Update
Tracking and caching mechanisms
The DbContext is lightweight and designed for short-lived use.
3. DbSet
Represents a table or view in the database.
It provides:
DbSet does not execute queries itself; instead, it passes expressions into the EF Core pipeline.
4. EF Core Model Metadata
EF Core constructs a metadata model describing:
Entity types
Keys and indexes
Properties
Relationships
Constraints
Conversions
This metadata is essential for:
SQL generation
Migrations
Validation
Runtime behavior
Relationship Handling in EF Core
EF Core supports all major relationship patterns:
1. One-to-One
One record links to exactly one other record.
2. One-to-Many
One record can have multiple related records.
3. Many-to-Many
Multiple entities relate with each other through an intermediate join table.
EF Core automatically manages:
Foreign key mappings
Cascading behaviors
Referential integrity
Navigation properties
Relationships are a core element of EF Core's ability to model real-world domains.
Migrations – What They Are and How They Work
Migrations allow EF Core to maintain a version history of your database structure.
What migrations do:
Track schema changes
Apply updates safely
Record history in migration files
Allow rollback/upgrade steps
Modify tables without losing data
Migrations ensure that the database and application evolve together over time.
Configuration in EF Core
EF Core supports configuration through:
1. Data Annotations
Attributes applied directly to entity properties.
2. Fluent API
Highly detailed configuration inside the DbContext.
Configuration controls:
Table names
Keys
Relationships
Column types
Default values
Indexes
Constraints
Fluent API provides the highest level of control for complex models.
Advanced EF Core Capabilities
EF Core includes several advanced, enterprise-grade features:
1. Concurrency Handling
EF Core supports optimistic concurrency to prevent data overwrites when multiple users update the same record simultaneously.
2. Shadow Properties
Properties not defined in the C# class but maintained by EF Core for metadata or internal use.
Useful for:
Tracking audit values
Internal IDs
Soft delete flags
3. Value Conversions
EF Core can convert data types between:
Example: Enum ←→ String
Example: Custom type ←→ JSON column
4. Global Query Filters
Allows defining filters applied automatically to all queries.
Used for:
Soft delete
Multi-tenancy
Status-based filtering
5. Interceptors
EF Core allows running custom logic before or after database calls.
Use cases:
Logging
Security
Auditing
Encryption
Multi-tenancy rules
Caching
6. Database Transactions
EF Core supports:
This ensures data integrity during multi-step operations.
Performance Characteristics of EF Core
EF Core includes multiple performance enhancements:
1. No Tracking Queries
When tracking isn’t needed, turning it off saves overhead.
2. Compiled Queries
Improves execution for repeating heavy queries.
3. Batching
Sends multiple SQL statements in a single round trip.
4. Efficient Change Detection
Only modified fields generate SQL updates.
5. Connection Pooling
Automatically reused, reducing overhead.
EF Core is significantly faster than older EF versions due to these optimizations.
Entity Framework Core is a foundational technology in modern .NET development. Its ability to abstract database interactions, manage schema evolution, track changes, optimize performance, handle relationships, manage transactions, and integrate seamlessly with dependency injection makes it one of the most powerful ORMs available.
By understanding EF Core’s internal architecture and capabilities, developers can build:
Clean
Maintainable
Scalable
Enterprise-ready
High-performance
applications with minimal effort.
EF Core continues to evolve with every .NET release, introducing new features that refine performance, flexibility, and developer productivity.
Thank you for reading this comprehensive guide on Entity Framework Core. EF Core is a major part of modern backend development, and mastering it provides a strong foundation for building elegant, scalable, and professional .NET applications.