What is Entity Framework Core, and how does it differ from Entity Framework?

Entity Framework Core (EF Core) is an open-source, lightweight, extensible, and cross-platform version of Microsoft’s popular Object-Relational Mapping (ORM) framework, Entity Framework (EF). EF Core allows developers to work with databases using .NET objects, eliminating most of the data-access code typically needed. It supports .NET Core applications as well as .NET Framework, enabling it to work with various databases and platforms.

Key Differences Between Entity Framework Core and Entity Framework

Entity Framework Core and Entity Framework (often referred to as "EF6") differ significantly in terms of features, architecture, and performance. Here are some main points of comparison:

1. Cross-Platform Compatibility

• EF Core: Built from the ground up to be cross-platform, supporting Linux, macOS, and Windows. It runs on .NET Core and the full .NET Framework.
• EF6: Primarily designed for .NET Framework and therefore mostly limited to Windows environments.

2. Performance Improvements

• EF Core: Optimized for better performance, especially with support for efficient querying and connection pooling. EF Core introduces features like batching of commands, which reduces the number of database round-trips and enhances performance.
• EF6: Known to be slower in comparison, as it lacks several of these performance optimizations.

3. Lightweight and Modular Design

• EF Core: Designed to be lightweight and modular, meaning you only load the components you need. This modularity allows developers to choose specific providers and extensions based on project requirements.
• EF6: A monolithic framework where all features and functionalities are included, which could add unnecessary overhead.

4. LINQ Query Translation Improvements

• EF Core: Has more efficient query translation, and supports LINQ in a way that avoids certain inefficiencies in EF6. It also provides better SQL generation, particularly for complex LINQ queries.
• EF6: Although it supports LINQ, EF6 can struggle with certain types of queries, sometimes leading to inefficient SQL that can negatively impact performance.

5. Features Supported

• EF Core:
  • Change Tracking: Works efficiently, including “No Tracking” queries for read-only operations, reducing memory usage.
  • Batching of Commands: Reduces database round-trips by batching similar commands together.
  • Shadow Properties: Properties that are part of the EF model but not part of the .NET entity class.
  • Global Query Filters: Allows you to define global filters, for instance, to filter out soft-deleted records.
  • Owned Types: Allows for complex types within an entity, commonly used for Value Objects in DDD.
• EF6:
  • EF6 includes features like automatic migrations and complex type mappings, which EF Core only added over time or handles differently.
  • Lazy Loading: EF6 has built-in support for lazy loading, whereas EF Core requires explicit configuration or proxies.

6. Migration Capabilities

• EF Core: Includes improved migration capabilities. However, it initially started with limited migration features, which have been gradually enhanced to support schema changes more flexibly.
• EF6: Has a robust migration system but does not offer some of the advanced capabilities and flexibility found in later EF Core versions.

7. Database Providers

• EF Core: Supports a wide range of databases with separate providers (e.g., SQL Server, SQLite, MySQL, PostgreSQL, Cosmos DB, etc.). EF Core is also more open to third-party database providers.
• EF6: Primarily focused on SQL Server, though other providers are available, but without the extensive cross-platform support seen in EF Core.

8. Support for NoSQL Databases

• EF Core: Introduced support for NoSQL databases, such as Cosmos DB, which allows developers to work with document databases in addition to relational databases.
• EF6: Limited to relational databases and lacks direct support for NoSQL databases.

Example of Basic Code in EF Core vs. EF6

Though basic usage remains similar between EF Core and EF6, there are some syntactic differences:

// EF Core
public class AppDbContext : DbContext
{
    public DbSet<Customer> Customers { get; set; }

    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    {
        optionsBuilder.UseSqlServer("YourConnectionString");
    }
}

// EF6
public class AppDbContext : DbContext
{
    public AppDbContext() : base("YourConnectionString") { }
    public DbSet<Customer> Customers { get; set; }
}

In EF Core, DbContextOptionsBuilder is used in OnConfiguring to specify the provider and connection string. In EF6, the connection string can be passed directly to the base DbContext constructor.

Conclusion

EF Core was designed as a high-performance, cross-platform replacement for EF6 with a more modular, lightweight, and flexible architecture. It is generally preferred for new applications, particularly those built on .NET Core or .NET 5+ that benefit from cross-platform capabilities and better performance. EF6, however, remains a reliable choice for applications that still depend on the full .NET Framework and Windows-only environments.