Announcing Entity Framework Core 5.0 Preview 3

Jeremy Likness

Jeremy

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

The third 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.3.20181.2

The EF Core packages published today are:

We have also published the 5.0 preview 3 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.3.20181.2

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

Entity Framework Core 5.0 Preview 3
Entity Framework Core 5.0 Preview 3 CLI

What’s new in EF Core 5 Preview 3

We maintain documentation covering new features introduced into each preview.

Some of the highlights from preview 3 are called out below.

Filtered Include

The Include method now supports filtering of the entities included.
For example:

var blogs = context.Blogs
    .Include(e => e.Posts.Where(p => p.Title.Contains("Cheese")))
    .ToList();

This query will return blogs together with each associated post, but only when the post title contains “Cheese”.

Skip and Take can also be used to reduce the number of included entities.
For example:

var blogs = context.Blogs
    .Include(e => e.Posts.OrderByDescending(post => post.Title).Take(5)))
    .ToList();

This query will return blogs with at most five posts included on each blog.

See the Include documentation for full details.

New ModelBuilder API for navigation properties

Navigation properties are primarily configured when defining relationships.
However, the new Navigation method can be used in the cases where navigation properties need additional configuration.
For example, to set a backing field for the navigation when the field would not be found by convention:

modelBuilder.Entity<Blog>().Navigation(e => e.Posts).HasField("_myposts");

Note that the Navigation API does not replace relationship configuration.
Instead it allows additional configuration of navigation properties in already discovered or defined relationships.

Documentation is tracked by issue #2302.

New command-line parameters for namespaces and connection strings

Migrations and scaffolding now allow namespaces to be specified on the command line.
For example, to reverse engineer a database putting the context and model classes in different namespaces:

dotnet ef dbcontext scaffold "connection string" Microsoft.EntityFrameworkCore.SqlServer --context-namespace "My.Context" --namespace "My.Model"

Also, a connection string can now be passed to the database-update command:

dotnet ef database update --connection "connection string"

Equivalent parameters have also been added to the PowerShell commands used in the VS Package Manager Console.

Documentation is tracked by issue #2303.

EnableDetailedErrors has returned

For performance reasons, EF doesn’t do additional null-checks when reading values from the database.
This can result in exceptions that are hard to root-cause when an unexpected null is encountered.

Using EnableDetailedErrors will add extra null checking to queries such that, for a small performance overhead, these errors are easier to trace back to a root cause.

For example:

protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    => optionsBuilder
        .EnableDetailedErrors()
        .EnableSensitiveDataLogging() // Often also useful with EnableDetailedErrors 
        .UseSqlServer(Your.SqlServerConnectionString);

Documentation is tracked by issue #955.

Cosmos partition keys

The partition key to use for a given query can now be specified in the query.
For example:

await context.Set<Customer>()
             .WithPartitionKey(myPartitionKey)
             .FirstAsync();

Documentation is tracked by issue #2199.

Support for the SQL Server DATALENGTH function

This can be accessed using the new EF.Functions.DataLength method.
For example:

var count = context.Orders.Count(c => 100 < EF.Functions.DataLength(c.OrderDate));

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

EF Core docs has a new landing page! The main page for Entity Framework documentation has been overhauled to provide you with a hub experience. We hope this new format helps you find the documentation you need faster and with fewer clicks.

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.


The following short links are provided for easy reference and access.

Main documentation:
https://aka.ms/efdocs

Issues and feature requests for EF Core:
https://aka.ms/efcorefeedback

Entity Framework Roadmap:
https://aka.ms/efroadmap

What’s new in EF Core 5.x?
https://aka.ms/efcore5


Thank you from the team

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

ajcvickers
Arthur Vickers
AndriySvyryd
Andriy Svyryd

Brice Lambson
JeremyLikness
Jeremy Likness
lajones
lajones
maumar
Maurycy Markowski
roji
Shay Rojansky
smitpatel
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! (List is in chronological order of first contribution to EF Core 5).

aevitas
aevitas
alaatm
Alaa Masoud
aleksandar-manukov
Aleksandar Manukov
amrbadawy
Amr Badawy
AnthonyMonterrosa
Anthony Monterrosa
bbrandt
Ben Brandt
benmccallum
Ben McCallum
ccjx
Clarence Cai
CGijbels
Christophe Gijbels
cincuranet
Jiri Cincura
Costo
Vincent Costel
dshuvaev
Dmitry Shuvaev
EricStG
Eric St-Georges
ErikEJ
Erik Ejlskov Jensen
gravbox
Christopher Davis
ivaylokenov
Ivaylo Kenov
jfoshee
Jacob Foshee
jmzagorski
Jeremy Zagorski
jviau
Jacob Viau
knom
Max K.
lohoris-crane
lohoris-crane
loic-sharma
Loïc Sharma
lokalmatador
lokalmatador
mariusGundersen
Marius Gundersen
Marusyk
Roman Marusyk
matthiaslischka
Matthias Lischka
MaxG117
MaxG117
MHDuke
MHDuke
mikes-gh
Mike Surcouf
Muppets
Neil Bostrom
nmichels
Nícolas Michels
OOberoi
Obi Oberoi
orionstudt
Josh Studt
ozantopal
Ozan Topal
pmiddleton
Paul Middleton
prog-rajkamal
Raj
ptjhuang
Peter Huang
ralmsdeveloper
Rafael Almeida Santos
redoz
Patrik Husfloen
rmarskell
Richard Marskell
sguitardude
sguitardude
SimpleSamples
Sam Hobbs
svengeance
Sven
VladDragnea
Vlad
vslee
vslee
WeihanLi
liweihan
Youssef1313
Youssef Victor
1iveowl
1iveowl
thomaslevesque
Thomas Levesque
akovac35
Aleksander Kovač
leotsarev
Leonid Tsarev
kostat
Konstantin Triger
sungam3r
Ivan Maximov
dzmitry-lahoda
Dzmitry Lahoda
Logerfo
Bruno Logerfo

1 comment

Leave a comment