Today, the .NET data team announces the fourth preview release of EF Core 7.0 (EF7). In addition to bug fixes and foundation work for larger features, this preview includes updates to ensure that converters and comparers are handled by type mapping and to support using converters with value generators. Be sure to read the full plan for EF7 to learn what’s on the roadmap.

Domain-driven design and “guarded” keys

One pattern from domain-driven design (DDD) is the concept of using value objects as keys. In other words, instead of declaring a key like this:

public class Thing
{
  public int Id { get; set; }
}

It might look like this instead:

public class Thing
{
  public ThingKey Id { get; set; }
}

public class ThingKey
{
  public ThingKey(Func<int> generator) => Id = generator();  
  public ThingKey(int id) => Id = id;
  public int Id { get; private set; }
}

There are several advantages to doing this. The first and perhaps most obvious is that it hides the implementation details of the key. If you decide that you’d prefer to consume the limitless resource of GUIDs instead the more limited and boringly sequential set of available integers, your refactoring will be much easier thanks to the buffer the key class provides. You are also able to guard the key from bad data with validations so someone doesn’t accidentally assign a negative value. Speaking of accidents, have you ever passed the wrong id to a method that takes a key? The compiler doesn’t care because it’s all ints … or bytes … or 1s and 0s … but if you’re using strongly-typed keys, you will be forced to provide the key that, cough “Dad Joke” cough* fits. Otherwise, the compiler will complain.

Whether or not you use this approach is of course up to you, but before preview 4 the choice was limited in EF Core. The most obvious way to translate from an entity to a scalar is to use a converter, but EF Core would throw an exception if you tried to assign a converter to a property flagged for value generation. That constraint has been lifted and more importantly, the code updated to ensure this case is handled properly. Thanks to the 81 of you who upvoted this issue, it was prioritized and is now ready for you to try out. Let us know if you’re using this feature and how it works for you!

Prerequisites

• EF7 currently targets .NET 6. This will likely be updated to .NET 7 as we near the release.
• EF7 will not run on .NET Framework.

EF7 is the successor to EF Core 6.0, not to be confused with EF6. If you are considering upgrading from EF6, please read our guide to port from EF6 to EF Core.

How to get EF7 previews

EF7 is distributed exclusively as a set of NuGet packages. For example, to add the SQL Server provider to your project, you can use the following command using the dotnet tool:

dotnet add package Microsoft.EntityFrameworkCore.SqlServer --version 7.0.0-preview.4.22229.2

This following table links to the preview 1 versions of the EF Core packages and describes what they are used for.

We also published the 7.0 preview 1 release of the Microsoft.Data.Sqlite.Core provider for ADO.NET.

Installing the EF7 Command Line Interface (CLI)

Before you can execute EF7 Core migration or scaffolding commands, you’ll have to install the CLI package as either a global or local tool.

To install the preview tool globally, install with:

dotnet tool install --global dotnet-ef --version 7.0.0-preview.4.22229.2 

If you already have the tool installed, you can upgrade it with the following command:

dotnet tool update --global dotnet-ef --version 7.0.0-preview.4.22229.2 

It’s possible to use this new version of the EF7 CLI with projects that use older versions of the EF Core runtime.

Daily builds

EF7 previews are aligned with .NET 7 previews. These previews tend to lag behind the latest work on EF7. Consider using the daily builds instead to get the most up-to-date EF7 features and bug fixes.

As with the previews, the daily builds require .NET 6.

The .NET Data Community Standup

The .NET data team is now live streaming every other Wednesday at 10am Pacific Time, 1pm Eastern Time, or 17:00 UTC. Join the stream to ask questions about the data-related topic of your choice, including the latest preview release.

• Watch our YouTube playlist of previous shows
• Visit the .NET Community Standup page to preview upcoming shows
• Submit your ideas for a guest, product, demo, or other content to cover

Documentation and Feedback

The starting point for all EF Core documentation is docs.microsoft.com/ef/.

Please file issues found and any other feedback on the dotnet/efcore GitHub repo.

Helpful Links

The following links are provided for easy reference and access.

• EF Core Community Standup Playlist: https://aka.ms/efstandups
• Main documentation: https://aka.ms/efdocs
• Issues and feature requests for EF Core: https://aka.ms/efcorefeedback
• Entity Framework Roadmap: https://aka.ms/efroadmap
• Bi-weekly updates: https://github.com/dotnet/efcore/issues/27185

Thank you from the team

A big thank you from the EF team to everyone who has used and contributed to EF over the years!

Welcome to EF7.