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update whats new for preview 1 #4953

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Feb 19, 2025
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update whats new for preview 1 #4953

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37 changes: 35 additions & 2 deletions entity-framework/core/what-is-new/ef-core-10.0/whatsnew.md
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Expand Up @@ -24,13 +24,40 @@ EF10 requires the .NET 10 SDK to build and requires the .NET 10 runtime to run.

## LINQ and SQL translation

<a name="support-left-join"></a>

### Support for the .NET 10 LeftJoin operator

`LEFT JOIN` is a common and useful operation when working with EF Core. In previous versions, implementing `LEFT JOIN` in LINQ was quite complicated, requiring `SelectMany`, `GroupJoin` and `DefaultIfEmpty` operations [in a particular configuration](/dotnet/csharp/linq/standard-query-operators/join-operations#perform-left-outer-joins).

.NET 10 adds first-class LINQ support for `LeftJoin` method, making those queries much simpler to write. EF Core recognizes the new method, so it can be used in EF LINQ queries instead of the old construct:

```C#
var query = context.Students
.LeftJoin(
context.Departments,
student => student.DepartmentID,
department => department.ID,
(student, department) => new
{
student.FirstName,
student.LastName,
Department = department.Name ?? "[NONE]"
});
```

See [#12793](https://github.com/dotnet/efcore/issues/12793) for more details.

<a name="other-query-improvements"></a>

### Other query improvements

* Translation for DateOnly.ToDateTime(timeOnly) ([#35194](https://github.com/dotnet/efcore/pull/35194), contributed by [@mseada94](https://github.com/mseada94)).
* Optimization for multiple consecutive `LIMIT`s ([#35384](https://github.com/dotnet/efcore/pull/35384)), contributed by [@ranma42](https://github.com/ranma42)).
* Optimization for use of `Count` operation on `ICollection<T>` ([#35381](https://github.com/dotnet/efcore/pull/35381)), contributed by [@ChrisJollyAU](https://github.com/ChrisJollyAU)).
* Optimization for multiple consecutive `LIMIT`s ([#35384](https://github.com/dotnet/efcore/pull/35384), contributed by [@ranma42](https://github.com/ranma42)).
* Optimization for use of `Count` operation on `ICollection<T>` ([#35381](https://github.com/dotnet/efcore/pull/35381), contributed by [@ChrisJollyAU](https://github.com/ChrisJollyAU)).
* Optimization for `MIN`/`MAX` over `DISTINCT` ([#34699](https://github.com/dotnet/efcore/pull/34699), contributed by [@ranma42](https://github.com/ranma42)).
* Translation for date/time functions using `DatePart.Microsecond` and `DatePart.Nanosecond` arguments ([#34861](https://github.com/dotnet/efcore/pull/34861)).
* Simplifying parameter names (e.g. from `@__city_0` to `city`) ([#35200](https://github.com/dotnet/efcore/pull/35200)).

## ExecuteUpdateAsync now accepts a regular, non-expression lambda

Expand Down Expand Up @@ -76,3 +103,9 @@ await context.Blogs.ExecuteUpdateAsync(s =>
```

Thanks to [@aradalvand](https://github.com/aradalvand) for proposing and pushing for this change (in [#32018](https://github.com/dotnet/efcore/issues/32018)).

<a name="other-improvements"></a>

## Other improvements

* Make SQL Server scaffolding compatible with Azure Data Explorer ([#34832](https://github.com/dotnet/efcore/pull/34832), contributed by [@barnuri](https://github.com/barnuri)).
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