Announcing Entity Framework Core 5.0 Preview 2

Jeremy Likness

Announcing Entity Framework Core 5.0 Preview 2

Today we are excited to announce the second preview release of EF Core 5.0.

The second previews of .NET 5 and ASP.NET Core 5.0 are also available now.

Prerequisites

The previews of EF Core 5.0 require .NET Standard 2.1. This means:

• EF Core 5.0 runs on .NET Core 3.1; it does not require .NET 5.
  • This may change in future previews depending on how the plan for .NET 5 evolves.
• EF Core 5.0 runs on other platforms that support .NET Standard 2.1.
• EF Core 5.0 will not run on .NET Standard 2.0 platforms, including .NET Framework.

How to get EF Core 5.0 previews

EF Core 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 5.0.0-preview.2.20159.4

The EF Core packages published today are:

• Microsoft.EntityFrameworkCore – The main EF Core package
• Microsoft.EntityFrameworkCore.SqlServer – Database provider for Microsoft SQL Server and SQL Azure
• Microsoft.EntityFrameworkCore.Sqlite – Database provider for SQLite
• Microsoft.EntityFrameworkCore.Cosmos – Database provider for Azure Cosmos DB
• Microsoft.EntityFrameworkCore.InMemory – The in-memory database provider
• Microsoft.EntityFrameworkCore.Tools – EF Core PowerShell commands for the Visual Studio Package Manager Console
• Microsoft.EntityFrameworkCore.Design – Shared design-time components for EF Core tools
• Microsoft.EntityFrameworkCore.SqlServer.NetTopologySuite – SQL Server support for spatial types
• Microsoft.EntityFrameworkCore.Sqlite.NetTopologySuite – SQLite support for spatial types
• Microsoft.EntityFrameworkCore.Proxies – Lazy-loading and change-tracking proxies
• Microsoft.EntityFrameworkCore.Abstractions – Decoupled EF Core abstractions
• Microsoft.EntityFrameworkCore.Relational – Shared EF Core components for relational database providers
• Microsoft.EntityFrameworkCore.Analyzers – C# analyzers for EF Core
• Microsoft.EntityFrameworkCore.Sqlite.Core – Database provider for SQLite without a packaged native binary

We have also published the 5.0 preview 2 release of the Microsoft.Data.Sqlite.Core ADO.NET provider.

Installing dotnet ef

As with EF Core 3.0 and 3.1, the dotnet ef command-line tool is no longer included in the .NET Core SDK. Before you can execute EF Core migration or scaffolding commands, you’ll have to install this package as either a global or local tool.

To install the preview tool globally, first uninstall any existing version with:

dotnet tool uninstall --global dotnet-ef

Then install with:

dotnet tool install --global dotnet-ef --version 5.0.0-preview.2.20159.4

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

What’s new in EF Core 5 Preview 2

We maintain documentation covering new features introduced into each preview.

Some of the highlights from preview 2 are called out below.

Use a C# attribute to specify a property backing field

A C# attribute can now be used to specify the backing field for a property. This allows EF Core to still write to and read from the backing field as would normally happen, even when the backing field cannot be found automatically. For example:

public class Blog
{
    private string _mainTitle;

    public int Id { get; set; }

    [BackingField(nameof(_mainTitle))]
    public string Title
    {
        get => _mainTitle;
        set => _mainTitle = value;
    }
}

Documentation is tracked by issue #2230.

Complete discriminator mapping

EF Core uses a discriminator column for TPH mapping of an inheritance hierarchy. Some performance enhancements are possible so long as EF Core knows all possible values for the discriminator. EF Core 5.0 now implements these enhancements.

For example, previous versions of EF Core would always generate this SQL for a query returning all types in a hierarchy:

SELECT [a].[Id], [a].[Discriminator], [a].[Name]
FROM [Animal] AS [a]
WHERE [a].[Discriminator] IN (N'Animal', N'Cat', N'Dog', N'Human')

EF Core 5.0 will now generate the following when a complete discriminator mapping is configured:

SELECT [a].[Id], [a].[Discriminator], [a].[Name]
FROM [Animal] AS [a]

This will be the default behavior starting with preview 3.

Performance improvements in Microsoft.Data.Sqlite

We have made two performance improvements for SQLIte:

• Retrieving binary and string data with GetBytes, GetChars, and GetTextReader is now more efficient by making use of SqliteBlob and streams.
• Initialization of SqliteConnection is now lazy.

These improvements are in the ADO.NET Microsoft.Data.Sqlite provider and hence also improve performance outside of EF Core.

Daily builds

EF Core previews are aligned with .NET 5 previews. These previews tend to lag behind the latest work on EF Core. Consider using the daily builds instead to get the most up-to-date EF Core features and bug fixes.

As with the previews, the daily builds do not require .NET 5; they can be used with GA/RTM release of .NET Core 3.1.

Documentation and feedback

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

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

Thank you from the team

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

Arthur Vickers	Andriy Svyryd	Brice Lambson	Jeremy Likness
lajones	Maurycy Markowski	Shay Rojansky	Smit Patel

Thank you to our contributors!

A big thank you to the following community members who have already contributed code or documentation to the EF Core 5 release!

aevitas	Alaa Masoud	Aleksandar Manukov	Amr Badawy
Anthony Monterrosa	Ben Brandt	Ben McCallum	Clarence Cai
Christophe Gijbels	Jiri Cincura	Vincent Costel	Dmitry Shuvaev
Eric St-Georges	Erik Ejlskov Jensen	Christopher Davis	Ivaylo Kenov
Jacob Foshee	Jeremy Zagorski	Jacob Viau	Max K.
lohoris-crane	Loïc Sharma	lokalmatador	Marius Gundersen
Roman Marusyk	Matthias Lischka	MaxG117	MHDuke
Mike Surcouf	Neil Bostrom	Nícolas Michels	Obi Oberoi
Josh Studt	Ozan Topal	Paul Middleton	Raj
Peter Huang	Rafael Almeida Santos	Patrik Husfloen	Richard Marskell
sguitardude	Sam Hobbs	Sven	Vlad
vslee	liweihan	Youssef Victor	1iveowl
Thomas Levesque	Aleksander Kovač	Leonid Tsarev	Konstantin Triger

Jeremy Likness Principal Program Manager - .NET Web Frameworks, .NET

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