Reinstate LINQ join convenience overloads and fix the build break - #126649

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eiriktsarpalis:fix/new-linq-join-methods
Apr 29, 2026
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Reinstate LINQ join convenience overloads and fix the build break#126649
eiriktsarpalis merged 6 commits into
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eiriktsarpalis:fix/new-linq-join-methods

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Reinstates the LINQ convenience overloads from #121998 and #121999 that were reverted in #126624, while also fixing the build break that caused the revert.

Summary

  • preserves the original API/implementation commits by cherry-picking them onto this branch
  • fixes the System.Linq.AsyncEnumerable test build break by making the affected async selectorless overload calls explicit where inference was insufficient during the multi-target build

Validation

  • build.cmd clr+libs -rc release
  • .\dotnet.cmd build .\src\libraries\System.Linq.AsyncEnumerable\tests\System.Linq.AsyncEnumerable.Tests.csproj /t:Test --no-restore
  • .\dotnet.cmd build .\src\libraries\System.Linq\tests\System.Linq.Tests.csproj /t:Test --no-restore
  • .\dotnet.cmd build .\src\libraries\System.Linq.Queryable\tests\System.Linq.Queryable.Tests.csproj /t:Test --no-restore

CopilotAIand others added 2 commits April 8, 2026 18:43
@eiriktsarpalis
@roji
Add Join/LeftJoin/RightJoin tuple overloads to LINQ APIs (dotnet#121998)
dc8035a
Implements tuple-returning overloads for `Join`, `LeftJoin`, and
`RightJoin` that eliminate the need for a `resultSelector` lambda when
you just want the joined elements as a tuple.
## Changes
- **System.Linq.Enumerable**: Added `Join<TOuter, TInner, TKey>`,
`LeftJoin<TOuter, TInner, TKey>`, `RightJoin<TOuter, TInner, TKey>`
returning `(TOuter Outer, TInner Inner)` tuples (with nullable element
for outer joins)
- **System.Linq.Queryable**: Added corresponding overloads with
`Expression<Func<>>` key selectors
- **System.Linq.AsyncEnumerable**: Added overloads for both sync and
async key selector variants
- All methods use a single overload with an optional
`IEqualityComparer<TKey>? comparer = null` parameter
## Example
Before:
```csharp
foreach (var (s, pair) in keys.Join(dict, k => k, p => p.Value, (outer, inner) => (outer, inner)))
Console.WriteLine(s + " : " + pair.Key);
```
After:
```csharp
foreach (var (s, pair) in keys.Join(dict, k => k, p => p.Value))
Console.WriteLine(s + " : " + pair.Key);
```
Fixesdotnet#120596
<!-- START COPILOT CODING AGENT SUFFIX -->
<details>
<summary>Original prompt</summary>
----
*This section details on the original issue you should resolve*
<issue_title>[API Proposal]: Linq Join return tuple similar to
Zip</issue_title>
<issue_description>### Background and motivation
For simplicity of `Join` it should just return `(TOuter,TInner)` instead
of the need for `resultSelector`
### API Proposal
```csharp
namespace System.Linq;
public static class Enumerable
{
public static IEnumerable<(TOuter Outer, TInner Inner)> Join<TOuter, TInner, TKey>(
this IEnumerable<TOuter> outer,
IEnumerable<TInner> inner,
Func<TOuter, TKey> outerKeySelector,
Func<TInner, TKey> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IEnumerable<(TOuter Outer, TInner? Inner)> LeftJoin<TOuter, TInner, TKey>(
this IEnumerable<TOuter> outer,
IEnumerable<TInner> inner,
Func<TOuter, TKey> outerKeySelector,
Func<TInner, TKey> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IEnumerable<(TOuter? Outer, TInner Inner)> RightJoin<TOuter, TInner, TKey>(
this IEnumerable<TOuter> outer,
IEnumerable<TInner> inner,
Func<TOuter, TKey> outerKeySelector,
Func<TInner, TKey> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
}
public static class Queryable
{
public static IQueryable<(TOuter Outer, TInner Inner)> Join<TOuter, TInner, TKey>(
this IQueryable<TOuter> outer,
IEnumerable<TInner> inner,
Expression<Func<TOuter, TKey>> outerKeySelector,
Expression<Func<TInner, TKey>> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IQueryable<(TOuter Outer, TInner? Inner)> LeftJoin<TOuter, TInner, TKey>(
this IQueryable<TOuter> outer,
IEnumerable<TInner> inner,
Expression<Func<TOuter, TKey>> outerKeySelector,
Expression<Func<TInner, TKey>> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IQueryable<(TOuter? Outer, TInner Inner)> RightJoin<TOuter, TInner, TKey>(
this IQueryable<TOuter> outer,
IEnumerable<TInner> inner,
Expression<Func<TOuter, TKey>> outerKeySelector,
Expression<Func<TInner, TKey>> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
}
public static class AsyncEnumerable
{
public static IAsyncEnumerable<(TOuter Outer, TInner Inner)> Join<TOuter, TInner, TKey>(
this IAsyncEnumerable<TOuter> outer,
IAsyncEnumerable<TInner> inner,
Func<TOuter, CancellationToken, ValueTask<TKey>> outerKeySelector,
Func<TInner, CancellationToken, ValueTask<TKey>> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IAsyncEnumerable<(TOuter Outer, TInner Inner)> Join<TOuter, TInner, TKey>(
this IAsyncEnumerable<TOuter> outer,
IAsyncEnumerable<TInner> inner,
Func<TOuter, TKey> outerKeySelector,
Func<TInner, TKey> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IAsyncEnumerable<(TOuter Outer, TInner? Inner)> LeftJoin<TOuter, TInner, TKey>(
this IAsyncEnumerable<TOuter> outer,
IAsyncEnumerable<TInner> inner,
Func<TOuter, CancellationToken, ValueTask<TKey>> outerKeySelector,
Func<TInner, CancellationToken, ValueTask<TKey>> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IAsyncEnumerable<(TOuter Outer, TInner? Inner)> LeftJoin<TOuter, TInner, TKey>(
this IAsyncEnumerable<TOuter> outer,
IAsyncEnumerable<TInner> inner,
Func<TOuter, TKey> outerKeySelector,
Func<TInner, TKey> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IAsyncEnumerable<(TOuter? Outer, TInner Inner)> RightJoin<TOuter, TInner, TKey>(
this IAsyncEnumerable<TOuter> outer,
IAsyncEnumerable<TInner> inner,
Func<TOuter, CancellationToken, ValueTask<TKey>> outerKeySelector,
Func<TInner, CancellationToken, ValueTask<TKey>> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IAsyncEnumerable<(TOuter? Outer, TInner Inner)> RightJoin<TOuter, TInner, TKey>(
this IAsyncEnumerable<TOuter> outer,
IAsyncEnumerable<TInner> inner,
Func<TOuter, TKey> outerKeySelector,
Func<TInner, TKey> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
}
```
### API Usage
```csharp
var keys = new[] { "x" ,"y" ,"z" };
var dict = new Dictionary<int,string>();
foreach (var (s,pair) in keys.Join(dict,(key) => key,(pair) => pair.Value))
Console.WriteLine(s + " : " pair.Key);
```
### Alternative Designs
Without this it need to make another lambda just for return tuple
```C#
foreach (var (s,pair) in keys.Join(dict,(key) => key,(pair) => pair.Value,(outer,inner) => (outer,inner)))
Console.WriteLine(s + " : " pair.Key);
```...
</details>
- Fixesdotnet#120596
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Co-authored-by: Shay Rojansky <roji@roji.org>
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Co-authored-by: Eirik Tsarpalis <eirik.tsarpalis@gmail.com>
(cherry picked from commit 2916d73)
@eiriktsarpalis@roji
Add GroupJoin overload returning IGrouping (dotnet#121999)
e3abcc5
Implements the approved API from dotnet#120587 — a simplified `GroupJoin`
overload that removes the need for an explicit result selector,
returning `IGrouping<TOuter, TInner>` where the outer element is the key
and the correlated inner elements are the grouping contents.
## Description
### API
```csharp
namespace System.Linq;
public static partial class Enumerable
{
public static IEnumerable<IGrouping<TOuter, TInner>> GroupJoin<TOuter, TInner, TKey>(
this IEnumerable<TOuter> outer,
IEnumerable<TInner> inner,
Func<TOuter, TKey> outerKeySelector,
Func<TInner, TKey> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
}
public static partial class Queryable
{
public static IQueryable<IGrouping<TOuter, TInner>> GroupJoin<TOuter, TInner, TKey>(
this IQueryable<TOuter> outer,
IEnumerable<TInner> inner,
Expression<Func<TOuter, TKey>> outerKeySelector,
Expression<Func<TInner, TKey>> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
}
public static partial class AsyncEnumerable
{
public static IAsyncEnumerable<IGrouping<TOuter, TInner>> GroupJoin<TOuter, TInner, TKey>(
this IAsyncEnumerable<TOuter> outer,
IAsyncEnumerable<TInner> inner,
Func<TOuter, TKey> outerKeySelector,
Func<TInner, TKey> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IAsyncEnumerable<IGrouping<TOuter, TInner>> GroupJoin<TOuter, TInner, TKey>(
this IAsyncEnumerable<TOuter> outer,
IAsyncEnumerable<TInner> inner,
Func<TOuter, CancellationToken, ValueTask<TKey>> outerKeySelector,
Func<TInner, CancellationToken, ValueTask<TKey>> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
}
```
### Changes
- **System.Linq**: New `GroupJoin<TOuter,TInner,TKey>` overload with
optional `IEqualityComparer<TKey>?` parameter + internal
`GroupJoinGrouping<TKey, TElement>` wrapper class. XML doc comments with
correct `<see cref="IGrouping{TOuter, TInner}"/>` references added to
the new public API.
- **System.Linq.Queryable**: New overload with optional
`IEqualityComparer<TKey>?` parameter and `[DynamicDependency]` on
`Enumerable.GroupJoin`3`. XML doc comments added.
- **System.Linq.AsyncEnumerable**: Two new overloads (sync and async key
selector variants) with optional `IEqualityComparer<TKey>?` parameter +
internal `AsyncGroupJoinGrouping<TKey, TElement>` wrapper class. XML doc
comments added.
- Reference assemblies updated for all three projects.
- Tests for all three projects, with `#if NET` guards in the async
enumerable tests for net481 compatibility (the new
`Enumerable.GroupJoin` overload and tuple-returning `Zip` are
unavailable on .NET Framework 4.8.1).
---------
Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: eiriktsarpalis <2813363+eiriktsarpalis@users.noreply.github.com>
Co-authored-by: Shay Rojansky <roji@roji.org>
Co-authored-by: roji <1862641+roji@users.noreply.github.com>
Co-authored-by: Eirik Tsarpalis <eirik.tsarpalis@gmail.com>
(cherry picked from commit 375857b)
CopilotAI review requested due to automatic review settings April 8, 2026 15:47
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Pull request overview

This PR reinstates previously reverted LINQ “convenience” overloads for Join/LeftJoin/RightJoin (tuple-returning) and GroupJoin (returning IGrouping without a result selector), and addresses the System.Linq.AsyncEnumerable multi-target test build break by making some overload calls more explicit.

Changes:

  • Add tuple-returning Join/LeftJoin/RightJoin overloads across Enumerable, Queryable, and AsyncEnumerable.
  • Add GroupJoin overload returning IEnumerable/IQueryable/IAsyncEnumerable<IGrouping<...>> without a resultSelector.
  • Extend/adjust tests and update reference assemblies to reflect the reinstated public APIs.

Reviewed changes

Copilot reviewed 24 out of 24 changed files in this pull request and generated no comments.

Show a summary per file
FileDescription
src/libraries/System.Linq/tests/RightJoinTests.csAdds coverage for tuple-returning Enumerable.RightJoin overload.
src/libraries/System.Linq/tests/LeftJoinTests.csAdds coverage for tuple-returning Enumerable.LeftJoin overload.
src/libraries/System.Linq/tests/JoinTests.csAdds coverage for tuple-returning Enumerable.Join overload.
src/libraries/System.Linq/tests/GroupJoinTests.csAdds coverage for selector-less Enumerable.GroupJoin returning IGrouping.
src/libraries/System.Linq/src/System/Linq/RightJoin.csImplements tuple-returning Enumerable.RightJoin overload and iterator.
src/libraries/System.Linq/src/System/Linq/LeftJoin.csImplements tuple-returning Enumerable.LeftJoin overload and iterator.
src/libraries/System.Linq/src/System/Linq/Join.csImplements tuple-returning Enumerable.Join overload and iterator.
src/libraries/System.Linq/src/System/Linq/GroupJoin.csImplements selector-less Enumerable.GroupJoin returning IGrouping + wrapper grouping type.
src/libraries/System.Linq/ref/System.Linq.csUpdates System.Linq reference assembly with new overloads.
src/libraries/System.Linq.Queryable/tests/RightJoinTests.csAdds coverage for tuple-returning Queryable.RightJoin overload.
src/libraries/System.Linq.Queryable/tests/LeftJoinTests.csAdds coverage for tuple-returning Queryable.LeftJoin overload.
src/libraries/System.Linq.Queryable/tests/JoinTests.csAdds coverage for tuple-returning Queryable.Join overload.
src/libraries/System.Linq.Queryable/tests/GroupJoinTests.csAdds coverage for selector-less Queryable.GroupJoin returning IGrouping.
src/libraries/System.Linq.Queryable/src/System/Linq/Queryable.csAdds Queryable overloads for tuple joins and selector-less GroupJoin (+ dependencies).
src/libraries/System.Linq.Queryable/ref/System.Linq.Queryable.csUpdates System.Linq.Queryable reference assembly with new overloads.
src/libraries/System.Linq.AsyncEnumerable/tests/RightJoinTests.csAdds tests for tuple-returning AsyncEnumerable.RightJoin and explicit-call patterns for multi-targeting.
src/libraries/System.Linq.AsyncEnumerable/tests/LeftJoinTests.csAdds tests for tuple-returning AsyncEnumerable.LeftJoin and explicit-call patterns for multi-targeting.
src/libraries/System.Linq.AsyncEnumerable/tests/JoinTests.csAdds tests for tuple-returning AsyncEnumerable.Join and explicit-call patterns for multi-targeting.
src/libraries/System.Linq.AsyncEnumerable/tests/GroupJoinTests.csAdds tests for selector-less AsyncEnumerable.GroupJoin returning IGrouping.
src/libraries/System.Linq.AsyncEnumerable/src/System/Linq/RightJoin.csImplements tuple-returning AsyncEnumerable.RightJoin overloads (sync+async key selectors).
src/libraries/System.Linq.AsyncEnumerable/src/System/Linq/LeftJoin.csImplements tuple-returning AsyncEnumerable.LeftJoin overloads (sync+async key selectors).
src/libraries/System.Linq.AsyncEnumerable/src/System/Linq/Join.csImplements tuple-returning AsyncEnumerable.Join overloads (sync+async key selectors).
src/libraries/System.Linq.AsyncEnumerable/src/System/Linq/GroupJoin.csImplements selector-less AsyncEnumerable.GroupJoin returning IGrouping + wrapper grouping type.
src/libraries/System.Linq.AsyncEnumerable/ref/System.Linq.AsyncEnumerable.csUpdates System.Linq.AsyncEnumerable reference assembly with new overloads.

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@eiriktsarpalis
eiriktsarpalisforce-pushed the fix/new-linq-join-methods branch from f53841d to 2ca6583CompareApril 9, 2026 16:23
@eiriktsarpalis
Fix failing AsyncEnumerable tests
bca206b
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@eiriktsarpalis
eiriktsarpalisforce-pushed the fix/new-linq-join-methods branch from 2ca6583 to bca206bCompareApril 9, 2026 16:24
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Pull request overview

Copilot reviewed 24 out of 24 changed files in this pull request and generated 7 comments.

Comment threadsrc/libraries/System.Linq/tests/RightJoinTests.cs
Comment threadsrc/libraries/System.Linq/tests/LeftJoinTests.cs
Comment threadsrc/libraries/System.Linq.Queryable/tests/RightJoinTests.cs
Comment threadsrc/libraries/System.Linq.Queryable/tests/RightJoinTests.cs
Comment threadsrc/libraries/System.Linq.Queryable/tests/LeftJoinTests.cs
Comment threadsrc/libraries/System.Linq.Queryable/tests/LeftJoinTests.cs
Comment threadsrc/libraries/System.Linq.AsyncEnumerable/tests/JoinTests.cs Outdated
@eiriktsarpalis
eiriktsarpalis requested a review from rojiApril 9, 2026 16:36
@eiriktsarpalis
Fix swapped tuple field order in JoinTests expected sequence
7cb9b7e
The resultSelector lambda had its parameter names swapped relative to
the actual (outer, inner) positions, producing reversed concatenation
in the expected sequence.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
This was referenced Apr 9, 2026
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LGTM, thanks!

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Copilot reviewed 24 out of 24 changed files in this pull request and generated no new comments.

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eiriktsarpalis enabled auto-merge (squash) April 29, 2026 10:03
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/ba-g test failures are unrelated.

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eiriktsarpalis merged commit 6df7b63 into dotnet:mainApr 29, 2026
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Reinstate LINQ join convenience overloads and fix the build break - #126649
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eiriktsarpalis merged 6 commits into
dotnet:mainfrom 
eiriktsarpalis:fix/new-linq-join-methods
Apr 29, 2026
Merged
Reinstate LINQ join convenience overloads and fix the build break#126649
eiriktsarpalis merged 6 commits into
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eiriktsarpalis:fix/new-linq-join-methods
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Note
This PR description was generated with Copilot.
Reinstates the LINQ convenience overloads from #121998 and #121999 that were reverted in #126624, while also fixing the build break that caused the revert.
Summary
  • preserves the original API/implementation commits by cherry-picking them onto this branch
  • fixes the System.Linq.AsyncEnumerable test build break by making the affected async selectorless overload calls explicit where inference was insufficient during the multi-target build
Validation
  • build.cmd clr+libs -rc release
  • .\dotnet.cmd build .\src\libraries\System.Linq.AsyncEnumerable\tests\System.Linq.AsyncEnumerable.Tests.csproj /t:Test --no-restore
  • .\dotnet.cmd build .\src\libraries\System.Linq\tests\System.Linq.Tests.csproj /t:Test --no-restore
  • .\dotnet.cmd build .\src\libraries\System.Linq.Queryable\tests\System.Linq.Queryable.Tests.csproj /t:Test --no-restore
CopilotAIand others
added 2 commits
April 8, 2026 18:43
@eiriktsarpalis
@roji
Add Join/LeftJoin/RightJoin tuple overloads to LINQ APIs (dotnet#121998)
dc8035a
Implements tuple-returning overloads for `Join`, `LeftJoin`, and
`RightJoin` that eliminate the need for a `resultSelector` lambda when
you just want the joined elements as a tuple.
## Changes
- **System.Linq.Enumerable**: Added `Join<TOuter, TInner, TKey>`,
`LeftJoin<TOuter, TInner, TKey>`, `RightJoin<TOuter, TInner, TKey>`
returning `(TOuter Outer, TInner Inner)` tuples (with nullable element
for outer joins)
- **System.Linq.Queryable**: Added corresponding overloads with
`Expression<Func<>>` key selectors
- **System.Linq.AsyncEnumerable**: Added overloads for both sync and
async key selector variants
- All methods use a single overload with an optional
`IEqualityComparer<TKey>? comparer = null` parameter
## Example
Before:
```csharp
foreach (var (s, pair) in keys.Join(dict, k => k, p => p.Value, (outer, inner) => (outer, inner)))
Console.WriteLine(s + " : " + pair.Key);
```
After:
```csharp
foreach (var (s, pair) in keys.Join(dict, k => k, p => p.Value))
Console.WriteLine(s + " : " + pair.Key);
```
Fixesdotnet#120596
<!-- START COPILOT CODING AGENT SUFFIX -->
<details>
<summary>Original prompt</summary>
----
*This section details on the original issue you should resolve*
<issue_title>[API Proposal]: Linq Join return tuple similar to
Zip</issue_title>
<issue_description>### Background and motivation
For simplicity of `Join` it should just return `(TOuter,TInner)` instead
of the need for `resultSelector`
### API Proposal
```csharp
namespace System.Linq;
public static class Enumerable
{
public static IEnumerable<(TOuter Outer, TInner Inner)> Join<TOuter, TInner, TKey>(
this IEnumerable<TOuter> outer,
IEnumerable<TInner> inner,
Func<TOuter, TKey> outerKeySelector,
Func<TInner, TKey> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IEnumerable<(TOuter Outer, TInner? Inner)> LeftJoin<TOuter, TInner, TKey>(
this IEnumerable<TOuter> outer,
IEnumerable<TInner> inner,
Func<TOuter, TKey> outerKeySelector,
Func<TInner, TKey> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IEnumerable<(TOuter? Outer, TInner Inner)> RightJoin<TOuter, TInner, TKey>(
this IEnumerable<TOuter> outer,
IEnumerable<TInner> inner,
Func<TOuter, TKey> outerKeySelector,
Func<TInner, TKey> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
}
public static class Queryable
{
public static IQueryable<(TOuter Outer, TInner Inner)> Join<TOuter, TInner, TKey>(
this IQueryable<TOuter> outer,
IEnumerable<TInner> inner,
Expression<Func<TOuter, TKey>> outerKeySelector,
Expression<Func<TInner, TKey>> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IQueryable<(TOuter Outer, TInner? Inner)> LeftJoin<TOuter, TInner, TKey>(
this IQueryable<TOuter> outer,
IEnumerable<TInner> inner,
Expression<Func<TOuter, TKey>> outerKeySelector,
Expression<Func<TInner, TKey>> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IQueryable<(TOuter? Outer, TInner Inner)> RightJoin<TOuter, TInner, TKey>(
this IQueryable<TOuter> outer,
IEnumerable<TInner> inner,
Expression<Func<TOuter, TKey>> outerKeySelector,
Expression<Func<TInner, TKey>> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
}
public static class AsyncEnumerable
{
public static IAsyncEnumerable<(TOuter Outer, TInner Inner)> Join<TOuter, TInner, TKey>(
this IAsyncEnumerable<TOuter> outer,
IAsyncEnumerable<TInner> inner,
Func<TOuter, CancellationToken, ValueTask<TKey>> outerKeySelector,
Func<TInner, CancellationToken, ValueTask<TKey>> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IAsyncEnumerable<(TOuter Outer, TInner Inner)> Join<TOuter, TInner, TKey>(
this IAsyncEnumerable<TOuter> outer,
IAsyncEnumerable<TInner> inner,
Func<TOuter, TKey> outerKeySelector,
Func<TInner, TKey> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IAsyncEnumerable<(TOuter Outer, TInner? Inner)> LeftJoin<TOuter, TInner, TKey>(
this IAsyncEnumerable<TOuter> outer,
IAsyncEnumerable<TInner> inner,
Func<TOuter, CancellationToken, ValueTask<TKey>> outerKeySelector,
Func<TInner, CancellationToken, ValueTask<TKey>> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IAsyncEnumerable<(TOuter Outer, TInner? Inner)> LeftJoin<TOuter, TInner, TKey>(
this IAsyncEnumerable<TOuter> outer,
IAsyncEnumerable<TInner> inner,
Func<TOuter, TKey> outerKeySelector,
Func<TInner, TKey> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IAsyncEnumerable<(TOuter? Outer, TInner Inner)> RightJoin<TOuter, TInner, TKey>(
this IAsyncEnumerable<TOuter> outer,
IAsyncEnumerable<TInner> inner,
Func<TOuter, CancellationToken, ValueTask<TKey>> outerKeySelector,
Func<TInner, CancellationToken, ValueTask<TKey>> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IAsyncEnumerable<(TOuter? Outer, TInner Inner)> RightJoin<TOuter, TInner, TKey>(
this IAsyncEnumerable<TOuter> outer,
IAsyncEnumerable<TInner> inner,
Func<TOuter, TKey> outerKeySelector,
Func<TInner, TKey> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
}
```
### API Usage
```csharp
var keys = new[] { "x" ,"y" ,"z" };
var dict = new Dictionary<int,string>();
foreach (var (s,pair) in keys.Join(dict,(key) => key,(pair) => pair.Value))
Console.WriteLine(s + " : " pair.Key);
```
### Alternative Designs
Without this it need to make another lambda just for return tuple
```C#
foreach (var (s,pair) in keys.Join(dict,(key) => key,(pair) => pair.Value,(outer,inner) => (outer,inner)))
Console.WriteLine(s + " : " pair.Key);
```...
</details>
- Fixesdotnet#120596
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Co-authored-by: Eirik Tsarpalis <eirik.tsarpalis@gmail.com>
(cherry picked from commit 2916d73)
@eiriktsarpalis@roji
Add GroupJoin overload returning IGrouping (dotnet#121999)
e3abcc5
Implements the approved API from dotnet#120587 — a simplified `GroupJoin`
overload that removes the need for an explicit result selector,
returning `IGrouping<TOuter, TInner>` where the outer element is the key
and the correlated inner elements are the grouping contents.
## Description
### API
```csharp
namespace System.Linq;
public static partial class Enumerable
{
public static IEnumerable<IGrouping<TOuter, TInner>> GroupJoin<TOuter, TInner, TKey>(
this IEnumerable<TOuter> outer,
IEnumerable<TInner> inner,
Func<TOuter, TKey> outerKeySelector,
Func<TInner, TKey> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
}
public static partial class Queryable
{
public static IQueryable<IGrouping<TOuter, TInner>> GroupJoin<TOuter, TInner, TKey>(
this IQueryable<TOuter> outer,
IEnumerable<TInner> inner,
Expression<Func<TOuter, TKey>> outerKeySelector,
Expression<Func<TInner, TKey>> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
}
public static partial class AsyncEnumerable
{
public static IAsyncEnumerable<IGrouping<TOuter, TInner>> GroupJoin<TOuter, TInner, TKey>(
this IAsyncEnumerable<TOuter> outer,
IAsyncEnumerable<TInner> inner,
Func<TOuter, TKey> outerKeySelector,
Func<TInner, TKey> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IAsyncEnumerable<IGrouping<TOuter, TInner>> GroupJoin<TOuter, TInner, TKey>(
this IAsyncEnumerable<TOuter> outer,
IAsyncEnumerable<TInner> inner,
Func<TOuter, CancellationToken, ValueTask<TKey>> outerKeySelector,
Func<TInner, CancellationToken, ValueTask<TKey>> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
}
```
### Changes
- **System.Linq**: New `GroupJoin<TOuter,TInner,TKey>` overload with
optional `IEqualityComparer<TKey>?` parameter + internal
`GroupJoinGrouping<TKey, TElement>` wrapper class. XML doc comments with
correct `<see cref="IGrouping{TOuter, TInner}"/>` references added to
the new public API.
- **System.Linq.Queryable**: New overload with optional
`IEqualityComparer<TKey>?` parameter and `[DynamicDependency]` on
`Enumerable.GroupJoin`3`. XML doc comments added.
- **System.Linq.AsyncEnumerable**: Two new overloads (sync and async key
selector variants) with optional `IEqualityComparer<TKey>?` parameter +
internal `AsyncGroupJoinGrouping<TKey, TElement>` wrapper class. XML doc
comments added.
- Reference assemblies updated for all three projects.
- Tests for all three projects, with `#if NET` guards in the async
enumerable tests for net481 compatibility (the new
`Enumerable.GroupJoin` overload and tuple-returning `Zip` are
unavailable on .NET Framework 4.8.1).
---------
Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: eiriktsarpalis <2813363+eiriktsarpalis@users.noreply.github.com>
Co-authored-by: Shay Rojansky <roji@roji.org>
Co-authored-by: roji <1862641+roji@users.noreply.github.com>
Co-authored-by: Eirik Tsarpalis <eirik.tsarpalis@gmail.com>
(cherry picked from commit 375857b)
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Pull request overview
This PR reinstates previously reverted LINQ “convenience” overloads for Join/LeftJoin/RightJoin (tuple-returning) and GroupJoin (returning IGrouping without a result selector), and addresses the System.Linq.AsyncEnumerable multi-target test build break by making some overload calls more explicit.
Changes:
  • Add tuple-returning Join/LeftJoin/RightJoin overloads across Enumerable, Queryable, and AsyncEnumerable.
  • Add GroupJoin overload returning IEnumerable/IQueryable/IAsyncEnumerable<IGrouping<...>> without a resultSelector.
  • Extend/adjust tests and update reference assemblies to reflect the reinstated public APIs.
Reviewed changes
Copilot reviewed 24 out of 24 changed files in this pull request and generated no comments.
Show a summary per file
FileDescription
src/libraries/System.Linq/tests/RightJoinTests.csAdds coverage for tuple-returning Enumerable.RightJoin overload.
src/libraries/System.Linq/tests/LeftJoinTests.csAdds coverage for tuple-returning Enumerable.LeftJoin overload.
src/libraries/System.Linq/tests/JoinTests.csAdds coverage for tuple-returning Enumerable.Join overload.
src/libraries/System.Linq/tests/GroupJoinTests.csAdds coverage for selector-less Enumerable.GroupJoin returning IGrouping.
src/libraries/System.Linq/src/System/Linq/RightJoin.csImplements tuple-returning Enumerable.RightJoin overload and iterator.
src/libraries/System.Linq/src/System/Linq/LeftJoin.csImplements tuple-returning Enumerable.LeftJoin overload and iterator.
src/libraries/System.Linq/src/System/Linq/Join.csImplements tuple-returning Enumerable.Join overload and iterator.
src/libraries/System.Linq/src/System/Linq/GroupJoin.csImplements selector-less Enumerable.GroupJoin returning IGrouping + wrapper grouping type.
src/libraries/System.Linq/ref/System.Linq.csUpdates System.Linq reference assembly with new overloads.
src/libraries/System.Linq.Queryable/tests/RightJoinTests.csAdds coverage for tuple-returning Queryable.RightJoin overload.
src/libraries/System.Linq.Queryable/tests/LeftJoinTests.csAdds coverage for tuple-returning Queryable.LeftJoin overload.
src/libraries/System.Linq.Queryable/tests/JoinTests.csAdds coverage for tuple-returning Queryable.Join overload.
src/libraries/System.Linq.Queryable/tests/GroupJoinTests.csAdds coverage for selector-less Queryable.GroupJoin returning IGrouping.
src/libraries/System.Linq.Queryable/src/System/Linq/Queryable.csAdds Queryable overloads for tuple joins and selector-less GroupJoin (+ dependencies).
src/libraries/System.Linq.Queryable/ref/System.Linq.Queryable.csUpdates System.Linq.Queryable reference assembly with new overloads.
src/libraries/System.Linq.AsyncEnumerable/tests/RightJoinTests.csAdds tests for tuple-returning AsyncEnumerable.RightJoin and explicit-call patterns for multi-targeting.
src/libraries/System.Linq.AsyncEnumerable/tests/LeftJoinTests.csAdds tests for tuple-returning AsyncEnumerable.LeftJoin and explicit-call patterns for multi-targeting.
src/libraries/System.Linq.AsyncEnumerable/tests/JoinTests.csAdds tests for tuple-returning AsyncEnumerable.Join and explicit-call patterns for multi-targeting.
src/libraries/System.Linq.AsyncEnumerable/tests/GroupJoinTests.csAdds tests for selector-less AsyncEnumerable.GroupJoin returning IGrouping.
src/libraries/System.Linq.AsyncEnumerable/src/System/Linq/RightJoin.csImplements tuple-returning AsyncEnumerable.RightJoin overloads (sync+async key selectors).
src/libraries/System.Linq.AsyncEnumerable/src/System/Linq/LeftJoin.csImplements tuple-returning AsyncEnumerable.LeftJoin overloads (sync+async key selectors).
src/libraries/System.Linq.AsyncEnumerable/src/System/Linq/Join.csImplements tuple-returning AsyncEnumerable.Join overloads (sync+async key selectors).
src/libraries/System.Linq.AsyncEnumerable/src/System/Linq/GroupJoin.csImplements selector-less AsyncEnumerable.GroupJoin returning IGrouping + wrapper grouping type.
src/libraries/System.Linq.AsyncEnumerable/ref/System.Linq.AsyncEnumerable.csUpdates System.Linq.AsyncEnumerable reference assembly with new overloads.
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Fix failing AsyncEnumerable tests
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Pull request overview
Copilot reviewed 24 out of 24 changed files in this pull request and generated 7 comments.
Comment threadsrc/libraries/System.Linq/tests/RightJoinTests.cs
Comment threadsrc/libraries/System.Linq/tests/LeftJoinTests.cs
Comment threadsrc/libraries/System.Linq.Queryable/tests/RightJoinTests.cs
Comment threadsrc/libraries/System.Linq.Queryable/tests/RightJoinTests.cs
Comment threadsrc/libraries/System.Linq.Queryable/tests/LeftJoinTests.cs
Comment threadsrc/libraries/System.Linq.Queryable/tests/LeftJoinTests.cs
Comment threadsrc/libraries/System.Linq.AsyncEnumerable/tests/JoinTests.cs
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from rojiApril 9, 2026 16:36
@eiriktsarpalis
Fix swapped tuple field order in JoinTests expected sequence
7cb9b7e
The resultSelector lambda had its parameter names swapped relative to
the actual (outer, inner) positions, producing reversed concatenation
in the expected sequence.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

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LGTM, thanks!
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, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Force GitHub README to respect dark mode\n(function() {\n var style = document.createElement('style');\n style.textContent = '\n .markdown-body {\n color-scheme: dark light;\n }\n .markdown-body pre { background: #161b22 !important; }\n .markdown-body code { background: rgba(110, 118, 129, 0.4) !important; }\n .markdown-body table th, .markdown-body table td { border-color: #30363d !important; }\n .markdown-body img { background: #0d1117; }\n .markdown-body blockquote { border-left-color: #8b949e; }\n .markdown-body hr { border-color: #30363d; }\n ';\n document.head.appendChild(style);\n})();", "GitHub Dark Mode README Fix");
}
} catch(__e) { console.warn('[Userscript:GitHub Dark Mode README Fix]', __e); }
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Reinstate LINQ join convenience overloads and fix the build break - #126649
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Apr 29, 2026
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Reinstate LINQ join convenience overloads and fix the build break#126649
eiriktsarpalis merged 6 commits into
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eiriktsarpalis:fix/new-linq-join-methods
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Note
This PR description was generated with Copilot.
Reinstates the LINQ convenience overloads from #121998 and #121999 that were reverted in #126624, while also fixing the build break that caused the revert.
Summary
  • preserves the original API/implementation commits by cherry-picking them onto this branch
  • fixes the System.Linq.AsyncEnumerable test build break by making the affected async selectorless overload calls explicit where inference was insufficient during the multi-target build
Validation
  • build.cmd clr+libs -rc release
  • .\dotnet.cmd build .\src\libraries\System.Linq.AsyncEnumerable\tests\System.Linq.AsyncEnumerable.Tests.csproj /t:Test --no-restore
  • .\dotnet.cmd build .\src\libraries\System.Linq\tests\System.Linq.Tests.csproj /t:Test --no-restore
  • .\dotnet.cmd build .\src\libraries\System.Linq.Queryable\tests\System.Linq.Queryable.Tests.csproj /t:Test --no-restore
CopilotAIand others
added 2 commits
April 8, 2026 18:43
@eiriktsarpalis
@roji
Add Join/LeftJoin/RightJoin tuple overloads to LINQ APIs (dotnet#121998)
dc8035a
Implements tuple-returning overloads for `Join`, `LeftJoin`, and
`RightJoin` that eliminate the need for a `resultSelector` lambda when
you just want the joined elements as a tuple.
## Changes
- **System.Linq.Enumerable**: Added `Join<TOuter, TInner, TKey>`,
`LeftJoin<TOuter, TInner, TKey>`, `RightJoin<TOuter, TInner, TKey>`
returning `(TOuter Outer, TInner Inner)` tuples (with nullable element
for outer joins)
- **System.Linq.Queryable**: Added corresponding overloads with
`Expression<Func<>>` key selectors
- **System.Linq.AsyncEnumerable**: Added overloads for both sync and
async key selector variants
- All methods use a single overload with an optional
`IEqualityComparer<TKey>? comparer = null` parameter
## Example
Before:
```csharp
foreach (var (s, pair) in keys.Join(dict, k => k, p => p.Value, (outer, inner) => (outer, inner)))
Console.WriteLine(s + " : " + pair.Key);
```
After:
```csharp
foreach (var (s, pair) in keys.Join(dict, k => k, p => p.Value))
Console.WriteLine(s + " : " + pair.Key);
```
Fixesdotnet#120596
<!-- START COPILOT CODING AGENT SUFFIX -->
<details>
<summary>Original prompt</summary>
----
*This section details on the original issue you should resolve*
<issue_title>[API Proposal]: Linq Join return tuple similar to
Zip</issue_title>
<issue_description>### Background and motivation
For simplicity of `Join` it should just return `(TOuter,TInner)` instead
of the need for `resultSelector`
### API Proposal
```csharp
namespace System.Linq;
public static class Enumerable
{
public static IEnumerable<(TOuter Outer, TInner Inner)> Join<TOuter, TInner, TKey>(
this IEnumerable<TOuter> outer,
IEnumerable<TInner> inner,
Func<TOuter, TKey> outerKeySelector,
Func<TInner, TKey> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IEnumerable<(TOuter Outer, TInner? Inner)> LeftJoin<TOuter, TInner, TKey>(
this IEnumerable<TOuter> outer,
IEnumerable<TInner> inner,
Func<TOuter, TKey> outerKeySelector,
Func<TInner, TKey> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IEnumerable<(TOuter? Outer, TInner Inner)> RightJoin<TOuter, TInner, TKey>(
this IEnumerable<TOuter> outer,
IEnumerable<TInner> inner,
Func<TOuter, TKey> outerKeySelector,
Func<TInner, TKey> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
}
public static class Queryable
{
public static IQueryable<(TOuter Outer, TInner Inner)> Join<TOuter, TInner, TKey>(
this IQueryable<TOuter> outer,
IEnumerable<TInner> inner,
Expression<Func<TOuter, TKey>> outerKeySelector,
Expression<Func<TInner, TKey>> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IQueryable<(TOuter Outer, TInner? Inner)> LeftJoin<TOuter, TInner, TKey>(
this IQueryable<TOuter> outer,
IEnumerable<TInner> inner,
Expression<Func<TOuter, TKey>> outerKeySelector,
Expression<Func<TInner, TKey>> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IQueryable<(TOuter? Outer, TInner Inner)> RightJoin<TOuter, TInner, TKey>(
this IQueryable<TOuter> outer,
IEnumerable<TInner> inner,
Expression<Func<TOuter, TKey>> outerKeySelector,
Expression<Func<TInner, TKey>> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
}
public static class AsyncEnumerable
{
public static IAsyncEnumerable<(TOuter Outer, TInner Inner)> Join<TOuter, TInner, TKey>(
this IAsyncEnumerable<TOuter> outer,
IAsyncEnumerable<TInner> inner,
Func<TOuter, CancellationToken, ValueTask<TKey>> outerKeySelector,
Func<TInner, CancellationToken, ValueTask<TKey>> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IAsyncEnumerable<(TOuter Outer, TInner Inner)> Join<TOuter, TInner, TKey>(
this IAsyncEnumerable<TOuter> outer,
IAsyncEnumerable<TInner> inner,
Func<TOuter, TKey> outerKeySelector,
Func<TInner, TKey> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IAsyncEnumerable<(TOuter Outer, TInner? Inner)> LeftJoin<TOuter, TInner, TKey>(
this IAsyncEnumerable<TOuter> outer,
IAsyncEnumerable<TInner> inner,
Func<TOuter, CancellationToken, ValueTask<TKey>> outerKeySelector,
Func<TInner, CancellationToken, ValueTask<TKey>> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IAsyncEnumerable<(TOuter Outer, TInner? Inner)> LeftJoin<TOuter, TInner, TKey>(
this IAsyncEnumerable<TOuter> outer,
IAsyncEnumerable<TInner> inner,
Func<TOuter, TKey> outerKeySelector,
Func<TInner, TKey> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IAsyncEnumerable<(TOuter? Outer, TInner Inner)> RightJoin<TOuter, TInner, TKey>(
this IAsyncEnumerable<TOuter> outer,
IAsyncEnumerable<TInner> inner,
Func<TOuter, CancellationToken, ValueTask<TKey>> outerKeySelector,
Func<TInner, CancellationToken, ValueTask<TKey>> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IAsyncEnumerable<(TOuter? Outer, TInner Inner)> RightJoin<TOuter, TInner, TKey>(
this IAsyncEnumerable<TOuter> outer,
IAsyncEnumerable<TInner> inner,
Func<TOuter, TKey> outerKeySelector,
Func<TInner, TKey> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
}
```
### API Usage
```csharp
var keys = new[] { "x" ,"y" ,"z" };
var dict = new Dictionary<int,string>();
foreach (var (s,pair) in keys.Join(dict,(key) => key,(pair) => pair.Value))
Console.WriteLine(s + " : " pair.Key);
```
### Alternative Designs
Without this it need to make another lambda just for return tuple
```C#
foreach (var (s,pair) in keys.Join(dict,(key) => key,(pair) => pair.Value,(outer,inner) => (outer,inner)))
Console.WriteLine(s + " : " pair.Key);
```...
</details>
- Fixesdotnet#120596
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(cherry picked from commit 2916d73)
@eiriktsarpalis@roji
Add GroupJoin overload returning IGrouping (dotnet#121999)
e3abcc5
Implements the approved API from dotnet#120587 — a simplified `GroupJoin`
overload that removes the need for an explicit result selector,
returning `IGrouping<TOuter, TInner>` where the outer element is the key
and the correlated inner elements are the grouping contents.
## Description
### API
```csharp
namespace System.Linq;
public static partial class Enumerable
{
public static IEnumerable<IGrouping<TOuter, TInner>> GroupJoin<TOuter, TInner, TKey>(
this IEnumerable<TOuter> outer,
IEnumerable<TInner> inner,
Func<TOuter, TKey> outerKeySelector,
Func<TInner, TKey> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
}
public static partial class Queryable
{
public static IQueryable<IGrouping<TOuter, TInner>> GroupJoin<TOuter, TInner, TKey>(
this IQueryable<TOuter> outer,
IEnumerable<TInner> inner,
Expression<Func<TOuter, TKey>> outerKeySelector,
Expression<Func<TInner, TKey>> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
}
public static partial class AsyncEnumerable
{
public static IAsyncEnumerable<IGrouping<TOuter, TInner>> GroupJoin<TOuter, TInner, TKey>(
this IAsyncEnumerable<TOuter> outer,
IAsyncEnumerable<TInner> inner,
Func<TOuter, TKey> outerKeySelector,
Func<TInner, TKey> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IAsyncEnumerable<IGrouping<TOuter, TInner>> GroupJoin<TOuter, TInner, TKey>(
this IAsyncEnumerable<TOuter> outer,
IAsyncEnumerable<TInner> inner,
Func<TOuter, CancellationToken, ValueTask<TKey>> outerKeySelector,
Func<TInner, CancellationToken, ValueTask<TKey>> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
}
```
### Changes
- **System.Linq**: New `GroupJoin<TOuter,TInner,TKey>` overload with
optional `IEqualityComparer<TKey>?` parameter + internal
`GroupJoinGrouping<TKey, TElement>` wrapper class. XML doc comments with
correct `<see cref="IGrouping{TOuter, TInner}"/>` references added to
the new public API.
- **System.Linq.Queryable**: New overload with optional
`IEqualityComparer<TKey>?` parameter and `[DynamicDependency]` on
`Enumerable.GroupJoin`3`. XML doc comments added.
- **System.Linq.AsyncEnumerable**: Two new overloads (sync and async key
selector variants) with optional `IEqualityComparer<TKey>?` parameter +
internal `AsyncGroupJoinGrouping<TKey, TElement>` wrapper class. XML doc
comments added.
- Reference assemblies updated for all three projects.
- Tests for all three projects, with `#if NET` guards in the async
enumerable tests for net481 compatibility (the new
`Enumerable.GroupJoin` overload and tuple-returning `Zip` are
unavailable on .NET Framework 4.8.1).
---------
Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: eiriktsarpalis <2813363+eiriktsarpalis@users.noreply.github.com>
Co-authored-by: Shay Rojansky <roji@roji.org>
Co-authored-by: roji <1862641+roji@users.noreply.github.com>
Co-authored-by: Eirik Tsarpalis <eirik.tsarpalis@gmail.com>
(cherry picked from commit 375857b)
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Pull request overview
This PR reinstates previously reverted LINQ “convenience” overloads for Join/LeftJoin/RightJoin (tuple-returning) and GroupJoin (returning IGrouping without a result selector), and addresses the System.Linq.AsyncEnumerable multi-target test build break by making some overload calls more explicit.
Changes:
  • Add tuple-returning Join/LeftJoin/RightJoin overloads across Enumerable, Queryable, and AsyncEnumerable.
  • Add GroupJoin overload returning IEnumerable/IQueryable/IAsyncEnumerable<IGrouping<...>> without a resultSelector.
  • Extend/adjust tests and update reference assemblies to reflect the reinstated public APIs.
Reviewed changes
Copilot reviewed 24 out of 24 changed files in this pull request and generated no comments.
Show a summary per file
FileDescription
src/libraries/System.Linq/tests/RightJoinTests.csAdds coverage for tuple-returning Enumerable.RightJoin overload.
src/libraries/System.Linq/tests/LeftJoinTests.csAdds coverage for tuple-returning Enumerable.LeftJoin overload.
src/libraries/System.Linq/tests/JoinTests.csAdds coverage for tuple-returning Enumerable.Join overload.
src/libraries/System.Linq/tests/GroupJoinTests.csAdds coverage for selector-less Enumerable.GroupJoin returning IGrouping.
src/libraries/System.Linq/src/System/Linq/RightJoin.csImplements tuple-returning Enumerable.RightJoin overload and iterator.
src/libraries/System.Linq/src/System/Linq/LeftJoin.csImplements tuple-returning Enumerable.LeftJoin overload and iterator.
src/libraries/System.Linq/src/System/Linq/Join.csImplements tuple-returning Enumerable.Join overload and iterator.
src/libraries/System.Linq/src/System/Linq/GroupJoin.csImplements selector-less Enumerable.GroupJoin returning IGrouping + wrapper grouping type.
src/libraries/System.Linq/ref/System.Linq.csUpdates System.Linq reference assembly with new overloads.
src/libraries/System.Linq.Queryable/tests/RightJoinTests.csAdds coverage for tuple-returning Queryable.RightJoin overload.
src/libraries/System.Linq.Queryable/tests/LeftJoinTests.csAdds coverage for tuple-returning Queryable.LeftJoin overload.
src/libraries/System.Linq.Queryable/tests/JoinTests.csAdds coverage for tuple-returning Queryable.Join overload.
src/libraries/System.Linq.Queryable/tests/GroupJoinTests.csAdds coverage for selector-less Queryable.GroupJoin returning IGrouping.
src/libraries/System.Linq.Queryable/src/System/Linq/Queryable.csAdds Queryable overloads for tuple joins and selector-less GroupJoin (+ dependencies).
src/libraries/System.Linq.Queryable/ref/System.Linq.Queryable.csUpdates System.Linq.Queryable reference assembly with new overloads.
src/libraries/System.Linq.AsyncEnumerable/tests/RightJoinTests.csAdds tests for tuple-returning AsyncEnumerable.RightJoin and explicit-call patterns for multi-targeting.
src/libraries/System.Linq.AsyncEnumerable/tests/LeftJoinTests.csAdds tests for tuple-returning AsyncEnumerable.LeftJoin and explicit-call patterns for multi-targeting.
src/libraries/System.Linq.AsyncEnumerable/tests/JoinTests.csAdds tests for tuple-returning AsyncEnumerable.Join and explicit-call patterns for multi-targeting.
src/libraries/System.Linq.AsyncEnumerable/tests/GroupJoinTests.csAdds tests for selector-less AsyncEnumerable.GroupJoin returning IGrouping.
src/libraries/System.Linq.AsyncEnumerable/src/System/Linq/RightJoin.csImplements tuple-returning AsyncEnumerable.RightJoin overloads (sync+async key selectors).
src/libraries/System.Linq.AsyncEnumerable/src/System/Linq/LeftJoin.csImplements tuple-returning AsyncEnumerable.LeftJoin overloads (sync+async key selectors).
src/libraries/System.Linq.AsyncEnumerable/src/System/Linq/Join.csImplements tuple-returning AsyncEnumerable.Join overloads (sync+async key selectors).
src/libraries/System.Linq.AsyncEnumerable/src/System/Linq/GroupJoin.csImplements selector-less AsyncEnumerable.GroupJoin returning IGrouping + wrapper grouping type.
src/libraries/System.Linq.AsyncEnumerable/ref/System.Linq.AsyncEnumerable.csUpdates System.Linq.AsyncEnumerable reference assembly with new overloads.
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Fix failing AsyncEnumerable tests
bca206b
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Pull request overview
Copilot reviewed 24 out of 24 changed files in this pull request and generated 7 comments.
Comment threadsrc/libraries/System.Linq/tests/RightJoinTests.cs
Comment threadsrc/libraries/System.Linq/tests/LeftJoinTests.cs
Comment threadsrc/libraries/System.Linq.Queryable/tests/RightJoinTests.cs
Comment threadsrc/libraries/System.Linq.Queryable/tests/RightJoinTests.cs
Comment threadsrc/libraries/System.Linq.Queryable/tests/LeftJoinTests.cs
Comment threadsrc/libraries/System.Linq.Queryable/tests/LeftJoinTests.cs
Comment threadsrc/libraries/System.Linq.AsyncEnumerable/tests/JoinTests.cs
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requested a review
from rojiApril 9, 2026 16:36
@eiriktsarpalis
Fix swapped tuple field order in JoinTests expected sequence
7cb9b7e
The resultSelector lambda had its parameter names swapped relative to
the actual (outer, inner) positions, producing reversed concatenation
in the expected sequence.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

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LGTM, thanks!
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, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Highlight search terms from Google/DuckDuckGo/Bing referrer\n(function() {\n var ref = document.referrer;\n var terms = [];\n \n if (ref.includes('google.com') || ref.includes('duckduckgo.com') || ref.includes('bing.com')) {\n var url = new URL(ref);\n var q = url.searchParams.get('q') || url.searchParams.get('p');\n if (q) {\n terms = q.split(/\\s+/).filter(function(t) { return t.length > 2; });\n }\n }\n \n if (terms.length === 0) return;\n \n var style = document.createElement('style');\n style.textContent = '.userscript-highlight { background: #fbbf24; color: #1a1a2e; padding: 1px 3px; border-radius: 2px; }';\n document.head.appendChild(style);\n \n function highlight(node) {\n if (node.nodeType === 3) { // text node\n var text = node.textContent;\n var found = false;\n terms.forEach(function(term) {\n var regex = new RegExp('(' + term.replace(/[.*+?^${}()|[\\]\\\\]/g, '\\\\') + ')', 'gi');\n if (regex.test(text)) {\n found = true;\n var frag = document.createDocumentFragment();\n var parts = text.split(regex);\n parts.forEach(function(part, i) {\n if (i % 2 === 0) {\n frag.appendChild(document.createTextNode(part));\n } else {\n var span = document.createElement('span');\n span.className = 'userscript-highlight';\n span.textContent = part;\n frag.appendChild(span);\n }\n });\n node.parentNode.replaceChild(frag, node);\n }\n });\n } else if (node.nodeType === 1 && node.childNodes) { // element\n var skipTags = ['SCRIPT', 'STYLE', 'NOSCRIPT', 'TEXTAREA', 'INPUT', 'SELECT'];\n if (!skipTags.includes(node.tagName)) {\n Array.from(node.childNodes).forEach(highlight);\n }\n }\n }\n \n highlight(document.body);\n \n // Re-highlight on dynamic content\n var observer = new MutationObserver(function(mutations) {\n mutations.forEach(function(m) {\n m.addedNodes.forEach(function(node) {\n if (node.nodeType === 1 || node.nodeType === 3) highlight(node);\n });\n });\n });\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Highlight Search Terms");
}
} catch(__e) { console.warn('[Userscript:Highlight Search Terms]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

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Reinstate LINQ join convenience overloads and fix the build break - #126649
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Apr 29, 2026
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Reinstate LINQ join convenience overloads and fix the build break#126649
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eiriktsarpalis:fix/new-linq-join-methods
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This PR description was generated with Copilot.
Reinstates the LINQ convenience overloads from #121998 and #121999 that were reverted in #126624, while also fixing the build break that caused the revert.
Summary
  • preserves the original API/implementation commits by cherry-picking them onto this branch
  • fixes the System.Linq.AsyncEnumerable test build break by making the affected async selectorless overload calls explicit where inference was insufficient during the multi-target build
Validation
  • build.cmd clr+libs -rc release
  • .\dotnet.cmd build .\src\libraries\System.Linq.AsyncEnumerable\tests\System.Linq.AsyncEnumerable.Tests.csproj /t:Test --no-restore
  • .\dotnet.cmd build .\src\libraries\System.Linq\tests\System.Linq.Tests.csproj /t:Test --no-restore
  • .\dotnet.cmd build .\src\libraries\System.Linq.Queryable\tests\System.Linq.Queryable.Tests.csproj /t:Test --no-restore
CopilotAIand others
added 2 commits
April 8, 2026 18:43
@eiriktsarpalis
@roji
Add Join/LeftJoin/RightJoin tuple overloads to LINQ APIs (dotnet#121998)
dc8035a
Implements tuple-returning overloads for `Join`, `LeftJoin`, and
`RightJoin` that eliminate the need for a `resultSelector` lambda when
you just want the joined elements as a tuple.
## Changes
- **System.Linq.Enumerable**: Added `Join<TOuter, TInner, TKey>`,
`LeftJoin<TOuter, TInner, TKey>`, `RightJoin<TOuter, TInner, TKey>`
returning `(TOuter Outer, TInner Inner)` tuples (with nullable element
for outer joins)
- **System.Linq.Queryable**: Added corresponding overloads with
`Expression<Func<>>` key selectors
- **System.Linq.AsyncEnumerable**: Added overloads for both sync and
async key selector variants
- All methods use a single overload with an optional
`IEqualityComparer<TKey>? comparer = null` parameter
## Example
Before:
```csharp
foreach (var (s, pair) in keys.Join(dict, k => k, p => p.Value, (outer, inner) => (outer, inner)))
Console.WriteLine(s + " : " + pair.Key);
```
After:
```csharp
foreach (var (s, pair) in keys.Join(dict, k => k, p => p.Value))
Console.WriteLine(s + " : " + pair.Key);
```
Fixesdotnet#120596
<!-- START COPILOT CODING AGENT SUFFIX -->
<details>
<summary>Original prompt</summary>
----
*This section details on the original issue you should resolve*
<issue_title>[API Proposal]: Linq Join return tuple similar to
Zip</issue_title>
<issue_description>### Background and motivation
For simplicity of `Join` it should just return `(TOuter,TInner)` instead
of the need for `resultSelector`
### API Proposal
```csharp
namespace System.Linq;
public static class Enumerable
{
public static IEnumerable<(TOuter Outer, TInner Inner)> Join<TOuter, TInner, TKey>(
this IEnumerable<TOuter> outer,
IEnumerable<TInner> inner,
Func<TOuter, TKey> outerKeySelector,
Func<TInner, TKey> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IEnumerable<(TOuter Outer, TInner? Inner)> LeftJoin<TOuter, TInner, TKey>(
this IEnumerable<TOuter> outer,
IEnumerable<TInner> inner,
Func<TOuter, TKey> outerKeySelector,
Func<TInner, TKey> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IEnumerable<(TOuter? Outer, TInner Inner)> RightJoin<TOuter, TInner, TKey>(
this IEnumerable<TOuter> outer,
IEnumerable<TInner> inner,
Func<TOuter, TKey> outerKeySelector,
Func<TInner, TKey> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
}
public static class Queryable
{
public static IQueryable<(TOuter Outer, TInner Inner)> Join<TOuter, TInner, TKey>(
this IQueryable<TOuter> outer,
IEnumerable<TInner> inner,
Expression<Func<TOuter, TKey>> outerKeySelector,
Expression<Func<TInner, TKey>> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IQueryable<(TOuter Outer, TInner? Inner)> LeftJoin<TOuter, TInner, TKey>(
this IQueryable<TOuter> outer,
IEnumerable<TInner> inner,
Expression<Func<TOuter, TKey>> outerKeySelector,
Expression<Func<TInner, TKey>> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IQueryable<(TOuter? Outer, TInner Inner)> RightJoin<TOuter, TInner, TKey>(
this IQueryable<TOuter> outer,
IEnumerable<TInner> inner,
Expression<Func<TOuter, TKey>> outerKeySelector,
Expression<Func<TInner, TKey>> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
}
public static class AsyncEnumerable
{
public static IAsyncEnumerable<(TOuter Outer, TInner Inner)> Join<TOuter, TInner, TKey>(
this IAsyncEnumerable<TOuter> outer,
IAsyncEnumerable<TInner> inner,
Func<TOuter, CancellationToken, ValueTask<TKey>> outerKeySelector,
Func<TInner, CancellationToken, ValueTask<TKey>> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IAsyncEnumerable<(TOuter Outer, TInner Inner)> Join<TOuter, TInner, TKey>(
this IAsyncEnumerable<TOuter> outer,
IAsyncEnumerable<TInner> inner,
Func<TOuter, TKey> outerKeySelector,
Func<TInner, TKey> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IAsyncEnumerable<(TOuter Outer, TInner? Inner)> LeftJoin<TOuter, TInner, TKey>(
this IAsyncEnumerable<TOuter> outer,
IAsyncEnumerable<TInner> inner,
Func<TOuter, CancellationToken, ValueTask<TKey>> outerKeySelector,
Func<TInner, CancellationToken, ValueTask<TKey>> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IAsyncEnumerable<(TOuter Outer, TInner? Inner)> LeftJoin<TOuter, TInner, TKey>(
this IAsyncEnumerable<TOuter> outer,
IAsyncEnumerable<TInner> inner,
Func<TOuter, TKey> outerKeySelector,
Func<TInner, TKey> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IAsyncEnumerable<(TOuter? Outer, TInner Inner)> RightJoin<TOuter, TInner, TKey>(
this IAsyncEnumerable<TOuter> outer,
IAsyncEnumerable<TInner> inner,
Func<TOuter, CancellationToken, ValueTask<TKey>> outerKeySelector,
Func<TInner, CancellationToken, ValueTask<TKey>> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IAsyncEnumerable<(TOuter? Outer, TInner Inner)> RightJoin<TOuter, TInner, TKey>(
this IAsyncEnumerable<TOuter> outer,
IAsyncEnumerable<TInner> inner,
Func<TOuter, TKey> outerKeySelector,
Func<TInner, TKey> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
}
```
### API Usage
```csharp
var keys = new[] { "x" ,"y" ,"z" };
var dict = new Dictionary<int,string>();
foreach (var (s,pair) in keys.Join(dict,(key) => key,(pair) => pair.Value))
Console.WriteLine(s + " : " pair.Key);
```
### Alternative Designs
Without this it need to make another lambda just for return tuple
```C#
foreach (var (s,pair) in keys.Join(dict,(key) => key,(pair) => pair.Value,(outer,inner) => (outer,inner)))
Console.WriteLine(s + " : " pair.Key);
```...
</details>
- Fixesdotnet#120596
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Co-authored-by: Shay Rojansky <roji@roji.org>
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Co-authored-by: Eirik Tsarpalis <eirik.tsarpalis@gmail.com>
(cherry picked from commit 2916d73)
@eiriktsarpalis@roji
Add GroupJoin overload returning IGrouping (dotnet#121999)
e3abcc5
Implements the approved API from dotnet#120587 — a simplified `GroupJoin`
overload that removes the need for an explicit result selector,
returning `IGrouping<TOuter, TInner>` where the outer element is the key
and the correlated inner elements are the grouping contents.
## Description
### API
```csharp
namespace System.Linq;
public static partial class Enumerable
{
public static IEnumerable<IGrouping<TOuter, TInner>> GroupJoin<TOuter, TInner, TKey>(
this IEnumerable<TOuter> outer,
IEnumerable<TInner> inner,
Func<TOuter, TKey> outerKeySelector,
Func<TInner, TKey> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
}
public static partial class Queryable
{
public static IQueryable<IGrouping<TOuter, TInner>> GroupJoin<TOuter, TInner, TKey>(
this IQueryable<TOuter> outer,
IEnumerable<TInner> inner,
Expression<Func<TOuter, TKey>> outerKeySelector,
Expression<Func<TInner, TKey>> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
}
public static partial class AsyncEnumerable
{
public static IAsyncEnumerable<IGrouping<TOuter, TInner>> GroupJoin<TOuter, TInner, TKey>(
this IAsyncEnumerable<TOuter> outer,
IAsyncEnumerable<TInner> inner,
Func<TOuter, TKey> outerKeySelector,
Func<TInner, TKey> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IAsyncEnumerable<IGrouping<TOuter, TInner>> GroupJoin<TOuter, TInner, TKey>(
this IAsyncEnumerable<TOuter> outer,
IAsyncEnumerable<TInner> inner,
Func<TOuter, CancellationToken, ValueTask<TKey>> outerKeySelector,
Func<TInner, CancellationToken, ValueTask<TKey>> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
}
```
### Changes
- **System.Linq**: New `GroupJoin<TOuter,TInner,TKey>` overload with
optional `IEqualityComparer<TKey>?` parameter + internal
`GroupJoinGrouping<TKey, TElement>` wrapper class. XML doc comments with
correct `<see cref="IGrouping{TOuter, TInner}"/>` references added to
the new public API.
- **System.Linq.Queryable**: New overload with optional
`IEqualityComparer<TKey>?` parameter and `[DynamicDependency]` on
`Enumerable.GroupJoin`3`. XML doc comments added.
- **System.Linq.AsyncEnumerable**: Two new overloads (sync and async key
selector variants) with optional `IEqualityComparer<TKey>?` parameter +
internal `AsyncGroupJoinGrouping<TKey, TElement>` wrapper class. XML doc
comments added.
- Reference assemblies updated for all three projects.
- Tests for all three projects, with `#if NET` guards in the async
enumerable tests for net481 compatibility (the new
`Enumerable.GroupJoin` overload and tuple-returning `Zip` are
unavailable on .NET Framework 4.8.1).
---------
Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: eiriktsarpalis <2813363+eiriktsarpalis@users.noreply.github.com>
Co-authored-by: Shay Rojansky <roji@roji.org>
Co-authored-by: roji <1862641+roji@users.noreply.github.com>
Co-authored-by: Eirik Tsarpalis <eirik.tsarpalis@gmail.com>
(cherry picked from commit 375857b)
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Pull request overview
This PR reinstates previously reverted LINQ “convenience” overloads for Join/LeftJoin/RightJoin (tuple-returning) and GroupJoin (returning IGrouping without a result selector), and addresses the System.Linq.AsyncEnumerable multi-target test build break by making some overload calls more explicit.
Changes:
  • Add tuple-returning Join/LeftJoin/RightJoin overloads across Enumerable, Queryable, and AsyncEnumerable.
  • Add GroupJoin overload returning IEnumerable/IQueryable/IAsyncEnumerable<IGrouping<...>> without a resultSelector.
  • Extend/adjust tests and update reference assemblies to reflect the reinstated public APIs.
Reviewed changes
Copilot reviewed 24 out of 24 changed files in this pull request and generated no comments.
Show a summary per file
FileDescription
src/libraries/System.Linq/tests/RightJoinTests.csAdds coverage for tuple-returning Enumerable.RightJoin overload.
src/libraries/System.Linq/tests/LeftJoinTests.csAdds coverage for tuple-returning Enumerable.LeftJoin overload.
src/libraries/System.Linq/tests/JoinTests.csAdds coverage for tuple-returning Enumerable.Join overload.
src/libraries/System.Linq/tests/GroupJoinTests.csAdds coverage for selector-less Enumerable.GroupJoin returning IGrouping.
src/libraries/System.Linq/src/System/Linq/RightJoin.csImplements tuple-returning Enumerable.RightJoin overload and iterator.
src/libraries/System.Linq/src/System/Linq/LeftJoin.csImplements tuple-returning Enumerable.LeftJoin overload and iterator.
src/libraries/System.Linq/src/System/Linq/Join.csImplements tuple-returning Enumerable.Join overload and iterator.
src/libraries/System.Linq/src/System/Linq/GroupJoin.csImplements selector-less Enumerable.GroupJoin returning IGrouping + wrapper grouping type.
src/libraries/System.Linq/ref/System.Linq.csUpdates System.Linq reference assembly with new overloads.
src/libraries/System.Linq.Queryable/tests/RightJoinTests.csAdds coverage for tuple-returning Queryable.RightJoin overload.
src/libraries/System.Linq.Queryable/tests/LeftJoinTests.csAdds coverage for tuple-returning Queryable.LeftJoin overload.
src/libraries/System.Linq.Queryable/tests/JoinTests.csAdds coverage for tuple-returning Queryable.Join overload.
src/libraries/System.Linq.Queryable/tests/GroupJoinTests.csAdds coverage for selector-less Queryable.GroupJoin returning IGrouping.
src/libraries/System.Linq.Queryable/src/System/Linq/Queryable.csAdds Queryable overloads for tuple joins and selector-less GroupJoin (+ dependencies).
src/libraries/System.Linq.Queryable/ref/System.Linq.Queryable.csUpdates System.Linq.Queryable reference assembly with new overloads.
src/libraries/System.Linq.AsyncEnumerable/tests/RightJoinTests.csAdds tests for tuple-returning AsyncEnumerable.RightJoin and explicit-call patterns for multi-targeting.
src/libraries/System.Linq.AsyncEnumerable/tests/LeftJoinTests.csAdds tests for tuple-returning AsyncEnumerable.LeftJoin and explicit-call patterns for multi-targeting.
src/libraries/System.Linq.AsyncEnumerable/tests/JoinTests.csAdds tests for tuple-returning AsyncEnumerable.Join and explicit-call patterns for multi-targeting.
src/libraries/System.Linq.AsyncEnumerable/tests/GroupJoinTests.csAdds tests for selector-less AsyncEnumerable.GroupJoin returning IGrouping.
src/libraries/System.Linq.AsyncEnumerable/src/System/Linq/RightJoin.csImplements tuple-returning AsyncEnumerable.RightJoin overloads (sync+async key selectors).
src/libraries/System.Linq.AsyncEnumerable/src/System/Linq/LeftJoin.csImplements tuple-returning AsyncEnumerable.LeftJoin overloads (sync+async key selectors).
src/libraries/System.Linq.AsyncEnumerable/src/System/Linq/Join.csImplements tuple-returning AsyncEnumerable.Join overloads (sync+async key selectors).
src/libraries/System.Linq.AsyncEnumerable/src/System/Linq/GroupJoin.csImplements selector-less AsyncEnumerable.GroupJoin returning IGrouping + wrapper grouping type.
src/libraries/System.Linq.AsyncEnumerable/ref/System.Linq.AsyncEnumerable.csUpdates System.Linq.AsyncEnumerable reference assembly with new overloads.
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Fix failing AsyncEnumerable tests
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Pull request overview
Copilot reviewed 24 out of 24 changed files in this pull request and generated 7 comments.
Comment threadsrc/libraries/System.Linq/tests/RightJoinTests.cs
Comment threadsrc/libraries/System.Linq/tests/LeftJoinTests.cs
Comment threadsrc/libraries/System.Linq.Queryable/tests/RightJoinTests.cs
Comment threadsrc/libraries/System.Linq.Queryable/tests/RightJoinTests.cs
Comment threadsrc/libraries/System.Linq.Queryable/tests/LeftJoinTests.cs
Comment threadsrc/libraries/System.Linq.Queryable/tests/LeftJoinTests.cs
Comment threadsrc/libraries/System.Linq.AsyncEnumerable/tests/JoinTests.cs
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from rojiApril 9, 2026 16:36
@eiriktsarpalis
Fix swapped tuple field order in JoinTests expected sequence
7cb9b7e
The resultSelector lambda had its parameter names swapped relative to
the actual (outer, inner) positions, producing reversed concatenation
in the expected sequence.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

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LGTM, thanks!
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, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Strip utm_, fbclid, gclid, etc. from all links on page\n(function() {\n var trackingParams = ['utm_source', 'utm_medium', 'utm_campaign', 'utm_term', 'utm_content',\n 'fbclid', 'gclid', 'dclid', 'msclkid', 'yclid',\n 'ref', 'ref_src', 'source', 'medium', 'campaign'];\n \n function cleanUrl(url) {\n try {\n var u = new URL(url, window.location.origin);\n var changed = false;\n trackingParams.forEach(function(p) {\n if (u.searchParams.has(p)) {\n u.searchParams.delete(p);\n changed = true;\n }\n });\n return changed ? u.toString() : url;\n } catch (e) {\n return url;\n }\n }\n \n function cleanLinks() {\n document.querySelectorAll('a[href]').forEach(function(a) {\n var clean = cleanUrl(a.href);\n if (clean !== a.href) a.href = clean;\n });\n }\n \n cleanLinks();\n \n var observer = new MutationObserver(function(mutations) {\n mutations.forEach(function(m) {\n m.addedNodes.forEach(function(node) {\n if (node.nodeType === 1) {\n if (node.tagName === 'A') cleanLinks();\n node.querySelectorAll('a[href]').forEach(function(a) {\n var clean = cleanUrl(a.href);\n if (clean !== a.href) a.href = clean;\n });\n }\n });\n });\n });\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Remove Tracking Parameters from Links");
}
} catch(__e) { console.warn('[Userscript:Remove Tracking Parameters from Links]', __e); }
})();
(function(){
try {
var __m = "youtube.com";
var __re = new RegExp('^' + "youtube\\.com" + '

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Reinstate LINQ join convenience overloads and fix the build break - #126649
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eiriktsarpalis:fix/new-linq-join-methods
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Reinstate LINQ join convenience overloads and fix the build break#126649
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eiriktsarpalis:fix/new-linq-join-methods
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This PR description was generated with Copilot.
Reinstates the LINQ convenience overloads from #121998 and #121999 that were reverted in #126624, while also fixing the build break that caused the revert.
Summary
  • preserves the original API/implementation commits by cherry-picking them onto this branch
  • fixes the System.Linq.AsyncEnumerable test build break by making the affected async selectorless overload calls explicit where inference was insufficient during the multi-target build
Validation
  • build.cmd clr+libs -rc release
  • .\dotnet.cmd build .\src\libraries\System.Linq.AsyncEnumerable\tests\System.Linq.AsyncEnumerable.Tests.csproj /t:Test --no-restore
  • .\dotnet.cmd build .\src\libraries\System.Linq\tests\System.Linq.Tests.csproj /t:Test --no-restore
  • .\dotnet.cmd build .\src\libraries\System.Linq.Queryable\tests\System.Linq.Queryable.Tests.csproj /t:Test --no-restore
CopilotAIand others
added 2 commits
April 8, 2026 18:43
@eiriktsarpalis
@roji
Add Join/LeftJoin/RightJoin tuple overloads to LINQ APIs (dotnet#121998)
dc8035a
Implements tuple-returning overloads for `Join`, `LeftJoin`, and
`RightJoin` that eliminate the need for a `resultSelector` lambda when
you just want the joined elements as a tuple.
## Changes
- **System.Linq.Enumerable**: Added `Join<TOuter, TInner, TKey>`,
`LeftJoin<TOuter, TInner, TKey>`, `RightJoin<TOuter, TInner, TKey>`
returning `(TOuter Outer, TInner Inner)` tuples (with nullable element
for outer joins)
- **System.Linq.Queryable**: Added corresponding overloads with
`Expression<Func<>>` key selectors
- **System.Linq.AsyncEnumerable**: Added overloads for both sync and
async key selector variants
- All methods use a single overload with an optional
`IEqualityComparer<TKey>? comparer = null` parameter
## Example
Before:
```csharp
foreach (var (s, pair) in keys.Join(dict, k => k, p => p.Value, (outer, inner) => (outer, inner)))
Console.WriteLine(s + " : " + pair.Key);
```
After:
```csharp
foreach (var (s, pair) in keys.Join(dict, k => k, p => p.Value))
Console.WriteLine(s + " : " + pair.Key);
```
Fixesdotnet#120596
<!-- START COPILOT CODING AGENT SUFFIX -->
<details>
<summary>Original prompt</summary>
----
*This section details on the original issue you should resolve*
<issue_title>[API Proposal]: Linq Join return tuple similar to
Zip</issue_title>
<issue_description>### Background and motivation
For simplicity of `Join` it should just return `(TOuter,TInner)` instead
of the need for `resultSelector`
### API Proposal
```csharp
namespace System.Linq;
public static class Enumerable
{
public static IEnumerable<(TOuter Outer, TInner Inner)> Join<TOuter, TInner, TKey>(
this IEnumerable<TOuter> outer,
IEnumerable<TInner> inner,
Func<TOuter, TKey> outerKeySelector,
Func<TInner, TKey> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IEnumerable<(TOuter Outer, TInner? Inner)> LeftJoin<TOuter, TInner, TKey>(
this IEnumerable<TOuter> outer,
IEnumerable<TInner> inner,
Func<TOuter, TKey> outerKeySelector,
Func<TInner, TKey> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IEnumerable<(TOuter? Outer, TInner Inner)> RightJoin<TOuter, TInner, TKey>(
this IEnumerable<TOuter> outer,
IEnumerable<TInner> inner,
Func<TOuter, TKey> outerKeySelector,
Func<TInner, TKey> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
}
public static class Queryable
{
public static IQueryable<(TOuter Outer, TInner Inner)> Join<TOuter, TInner, TKey>(
this IQueryable<TOuter> outer,
IEnumerable<TInner> inner,
Expression<Func<TOuter, TKey>> outerKeySelector,
Expression<Func<TInner, TKey>> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IQueryable<(TOuter Outer, TInner? Inner)> LeftJoin<TOuter, TInner, TKey>(
this IQueryable<TOuter> outer,
IEnumerable<TInner> inner,
Expression<Func<TOuter, TKey>> outerKeySelector,
Expression<Func<TInner, TKey>> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IQueryable<(TOuter? Outer, TInner Inner)> RightJoin<TOuter, TInner, TKey>(
this IQueryable<TOuter> outer,
IEnumerable<TInner> inner,
Expression<Func<TOuter, TKey>> outerKeySelector,
Expression<Func<TInner, TKey>> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
}
public static class AsyncEnumerable
{
public static IAsyncEnumerable<(TOuter Outer, TInner Inner)> Join<TOuter, TInner, TKey>(
this IAsyncEnumerable<TOuter> outer,
IAsyncEnumerable<TInner> inner,
Func<TOuter, CancellationToken, ValueTask<TKey>> outerKeySelector,
Func<TInner, CancellationToken, ValueTask<TKey>> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IAsyncEnumerable<(TOuter Outer, TInner Inner)> Join<TOuter, TInner, TKey>(
this IAsyncEnumerable<TOuter> outer,
IAsyncEnumerable<TInner> inner,
Func<TOuter, TKey> outerKeySelector,
Func<TInner, TKey> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IAsyncEnumerable<(TOuter Outer, TInner? Inner)> LeftJoin<TOuter, TInner, TKey>(
this IAsyncEnumerable<TOuter> outer,
IAsyncEnumerable<TInner> inner,
Func<TOuter, CancellationToken, ValueTask<TKey>> outerKeySelector,
Func<TInner, CancellationToken, ValueTask<TKey>> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IAsyncEnumerable<(TOuter Outer, TInner? Inner)> LeftJoin<TOuter, TInner, TKey>(
this IAsyncEnumerable<TOuter> outer,
IAsyncEnumerable<TInner> inner,
Func<TOuter, TKey> outerKeySelector,
Func<TInner, TKey> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IAsyncEnumerable<(TOuter? Outer, TInner Inner)> RightJoin<TOuter, TInner, TKey>(
this IAsyncEnumerable<TOuter> outer,
IAsyncEnumerable<TInner> inner,
Func<TOuter, CancellationToken, ValueTask<TKey>> outerKeySelector,
Func<TInner, CancellationToken, ValueTask<TKey>> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IAsyncEnumerable<(TOuter? Outer, TInner Inner)> RightJoin<TOuter, TInner, TKey>(
this IAsyncEnumerable<TOuter> outer,
IAsyncEnumerable<TInner> inner,
Func<TOuter, TKey> outerKeySelector,
Func<TInner, TKey> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
}
```
### API Usage
```csharp
var keys = new[] { "x" ,"y" ,"z" };
var dict = new Dictionary<int,string>();
foreach (var (s,pair) in keys.Join(dict,(key) => key,(pair) => pair.Value))
Console.WriteLine(s + " : " pair.Key);
```
### Alternative Designs
Without this it need to make another lambda just for return tuple
```C#
foreach (var (s,pair) in keys.Join(dict,(key) => key,(pair) => pair.Value,(outer,inner) => (outer,inner)))
Console.WriteLine(s + " : " pair.Key);
```...
</details>
- Fixesdotnet#120596
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Co-authored-by: Shay Rojansky <roji@roji.org>
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Co-authored-by: Eirik Tsarpalis <eirik.tsarpalis@gmail.com>
(cherry picked from commit 2916d73)
@eiriktsarpalis@roji
Add GroupJoin overload returning IGrouping (dotnet#121999)
e3abcc5
Implements the approved API from dotnet#120587 — a simplified `GroupJoin`
overload that removes the need for an explicit result selector,
returning `IGrouping<TOuter, TInner>` where the outer element is the key
and the correlated inner elements are the grouping contents.
## Description
### API
```csharp
namespace System.Linq;
public static partial class Enumerable
{
public static IEnumerable<IGrouping<TOuter, TInner>> GroupJoin<TOuter, TInner, TKey>(
this IEnumerable<TOuter> outer,
IEnumerable<TInner> inner,
Func<TOuter, TKey> outerKeySelector,
Func<TInner, TKey> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
}
public static partial class Queryable
{
public static IQueryable<IGrouping<TOuter, TInner>> GroupJoin<TOuter, TInner, TKey>(
this IQueryable<TOuter> outer,
IEnumerable<TInner> inner,
Expression<Func<TOuter, TKey>> outerKeySelector,
Expression<Func<TInner, TKey>> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
}
public static partial class AsyncEnumerable
{
public static IAsyncEnumerable<IGrouping<TOuter, TInner>> GroupJoin<TOuter, TInner, TKey>(
this IAsyncEnumerable<TOuter> outer,
IAsyncEnumerable<TInner> inner,
Func<TOuter, TKey> outerKeySelector,
Func<TInner, TKey> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IAsyncEnumerable<IGrouping<TOuter, TInner>> GroupJoin<TOuter, TInner, TKey>(
this IAsyncEnumerable<TOuter> outer,
IAsyncEnumerable<TInner> inner,
Func<TOuter, CancellationToken, ValueTask<TKey>> outerKeySelector,
Func<TInner, CancellationToken, ValueTask<TKey>> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
}
```
### Changes
- **System.Linq**: New `GroupJoin<TOuter,TInner,TKey>` overload with
optional `IEqualityComparer<TKey>?` parameter + internal
`GroupJoinGrouping<TKey, TElement>` wrapper class. XML doc comments with
correct `<see cref="IGrouping{TOuter, TInner}"/>` references added to
the new public API.
- **System.Linq.Queryable**: New overload with optional
`IEqualityComparer<TKey>?` parameter and `[DynamicDependency]` on
`Enumerable.GroupJoin`3`. XML doc comments added.
- **System.Linq.AsyncEnumerable**: Two new overloads (sync and async key
selector variants) with optional `IEqualityComparer<TKey>?` parameter +
internal `AsyncGroupJoinGrouping<TKey, TElement>` wrapper class. XML doc
comments added.
- Reference assemblies updated for all three projects.
- Tests for all three projects, with `#if NET` guards in the async
enumerable tests for net481 compatibility (the new
`Enumerable.GroupJoin` overload and tuple-returning `Zip` are
unavailable on .NET Framework 4.8.1).
---------
Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: eiriktsarpalis <2813363+eiriktsarpalis@users.noreply.github.com>
Co-authored-by: Shay Rojansky <roji@roji.org>
Co-authored-by: roji <1862641+roji@users.noreply.github.com>
Co-authored-by: Eirik Tsarpalis <eirik.tsarpalis@gmail.com>
(cherry picked from commit 375857b)
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Pull request overview
This PR reinstates previously reverted LINQ “convenience” overloads for Join/LeftJoin/RightJoin (tuple-returning) and GroupJoin (returning IGrouping without a result selector), and addresses the System.Linq.AsyncEnumerable multi-target test build break by making some overload calls more explicit.
Changes:
  • Add tuple-returning Join/LeftJoin/RightJoin overloads across Enumerable, Queryable, and AsyncEnumerable.
  • Add GroupJoin overload returning IEnumerable/IQueryable/IAsyncEnumerable<IGrouping<...>> without a resultSelector.
  • Extend/adjust tests and update reference assemblies to reflect the reinstated public APIs.
Reviewed changes
Copilot reviewed 24 out of 24 changed files in this pull request and generated no comments.
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FileDescription
src/libraries/System.Linq/tests/RightJoinTests.csAdds coverage for tuple-returning Enumerable.RightJoin overload.
src/libraries/System.Linq/tests/LeftJoinTests.csAdds coverage for tuple-returning Enumerable.LeftJoin overload.
src/libraries/System.Linq/tests/JoinTests.csAdds coverage for tuple-returning Enumerable.Join overload.
src/libraries/System.Linq/tests/GroupJoinTests.csAdds coverage for selector-less Enumerable.GroupJoin returning IGrouping.
src/libraries/System.Linq/src/System/Linq/RightJoin.csImplements tuple-returning Enumerable.RightJoin overload and iterator.
src/libraries/System.Linq/src/System/Linq/LeftJoin.csImplements tuple-returning Enumerable.LeftJoin overload and iterator.
src/libraries/System.Linq/src/System/Linq/Join.csImplements tuple-returning Enumerable.Join overload and iterator.
src/libraries/System.Linq/src/System/Linq/GroupJoin.csImplements selector-less Enumerable.GroupJoin returning IGrouping + wrapper grouping type.
src/libraries/System.Linq/ref/System.Linq.csUpdates System.Linq reference assembly with new overloads.
src/libraries/System.Linq.Queryable/tests/RightJoinTests.csAdds coverage for tuple-returning Queryable.RightJoin overload.
src/libraries/System.Linq.Queryable/tests/LeftJoinTests.csAdds coverage for tuple-returning Queryable.LeftJoin overload.
src/libraries/System.Linq.Queryable/tests/JoinTests.csAdds coverage for tuple-returning Queryable.Join overload.
src/libraries/System.Linq.Queryable/tests/GroupJoinTests.csAdds coverage for selector-less Queryable.GroupJoin returning IGrouping.
src/libraries/System.Linq.Queryable/src/System/Linq/Queryable.csAdds Queryable overloads for tuple joins and selector-less GroupJoin (+ dependencies).
src/libraries/System.Linq.Queryable/ref/System.Linq.Queryable.csUpdates System.Linq.Queryable reference assembly with new overloads.
src/libraries/System.Linq.AsyncEnumerable/tests/RightJoinTests.csAdds tests for tuple-returning AsyncEnumerable.RightJoin and explicit-call patterns for multi-targeting.
src/libraries/System.Linq.AsyncEnumerable/tests/LeftJoinTests.csAdds tests for tuple-returning AsyncEnumerable.LeftJoin and explicit-call patterns for multi-targeting.
src/libraries/System.Linq.AsyncEnumerable/tests/JoinTests.csAdds tests for tuple-returning AsyncEnumerable.Join and explicit-call patterns for multi-targeting.
src/libraries/System.Linq.AsyncEnumerable/tests/GroupJoinTests.csAdds tests for selector-less AsyncEnumerable.GroupJoin returning IGrouping.
src/libraries/System.Linq.AsyncEnumerable/src/System/Linq/RightJoin.csImplements tuple-returning AsyncEnumerable.RightJoin overloads (sync+async key selectors).
src/libraries/System.Linq.AsyncEnumerable/src/System/Linq/LeftJoin.csImplements tuple-returning AsyncEnumerable.LeftJoin overloads (sync+async key selectors).
src/libraries/System.Linq.AsyncEnumerable/src/System/Linq/Join.csImplements tuple-returning AsyncEnumerable.Join overloads (sync+async key selectors).
src/libraries/System.Linq.AsyncEnumerable/src/System/Linq/GroupJoin.csImplements selector-less AsyncEnumerable.GroupJoin returning IGrouping + wrapper grouping type.
src/libraries/System.Linq.AsyncEnumerable/ref/System.Linq.AsyncEnumerable.csUpdates System.Linq.AsyncEnumerable reference assembly with new overloads.
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Fix failing AsyncEnumerable tests
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Pull request overview
Copilot reviewed 24 out of 24 changed files in this pull request and generated 7 comments.
Comment threadsrc/libraries/System.Linq/tests/RightJoinTests.cs
Comment threadsrc/libraries/System.Linq/tests/LeftJoinTests.cs
Comment threadsrc/libraries/System.Linq.Queryable/tests/RightJoinTests.cs
Comment threadsrc/libraries/System.Linq.Queryable/tests/RightJoinTests.cs
Comment threadsrc/libraries/System.Linq.Queryable/tests/LeftJoinTests.cs
Comment threadsrc/libraries/System.Linq.Queryable/tests/LeftJoinTests.cs
Comment threadsrc/libraries/System.Linq.AsyncEnumerable/tests/JoinTests.cs
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from rojiApril 9, 2026 16:36
@eiriktsarpalis
Fix swapped tuple field order in JoinTests expected sequence
7cb9b7e
The resultSelector lambda had its parameter names swapped relative to
the actual (outer, inner) positions, producing reversed concatenation
in the expected sequence.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

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LGTM, thanks!
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Pull request overview
Copilot reviewed 24 out of 24 changed files in this pull request and generated no new comments.

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if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Auto-enable theater mode on YouTube\n(function() {\n function tryTheater() {\n var btn = document.querySelector('button[aria-label=\"Theater mode\"], ytd-player #player button[title=\"Theater mode\"]');\n if (btn && !btn.classList.contains('activated')) {\n btn.click();\n }\n }\n \n // Try immediately\n tryTheater();\n \n // Try after navigation (SPA)\n var lastUrl = location.href;\n setInterval(function() {\n if (location.href !== lastUrl) {\n lastUrl = location.href;\n setTimeout(tryTheater, 500);\n }\n }, 1000);\n \n // Also try on player load\n var observer = new MutationObserver(tryTheater);\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "YouTube Theater Mode Default");
}
} catch(__e) { console.warn('[Userscript:YouTube Theater Mode Default]', __e); }
})();
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try {
var __m = "*";
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Reinstate LINQ join convenience overloads and fix the build break - #126649
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eiriktsarpalis:fix/new-linq-join-methods
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Reinstate LINQ join convenience overloads and fix the build break#126649
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eiriktsarpalis:fix/new-linq-join-methods
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This PR description was generated with Copilot.
Reinstates the LINQ convenience overloads from #121998 and #121999 that were reverted in #126624, while also fixing the build break that caused the revert.
Summary
  • preserves the original API/implementation commits by cherry-picking them onto this branch
  • fixes the System.Linq.AsyncEnumerable test build break by making the affected async selectorless overload calls explicit where inference was insufficient during the multi-target build
Validation
  • build.cmd clr+libs -rc release
  • .\dotnet.cmd build .\src\libraries\System.Linq.AsyncEnumerable\tests\System.Linq.AsyncEnumerable.Tests.csproj /t:Test --no-restore
  • .\dotnet.cmd build .\src\libraries\System.Linq\tests\System.Linq.Tests.csproj /t:Test --no-restore
  • .\dotnet.cmd build .\src\libraries\System.Linq.Queryable\tests\System.Linq.Queryable.Tests.csproj /t:Test --no-restore
CopilotAIand others
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April 8, 2026 18:43
@eiriktsarpalis
@roji
Add Join/LeftJoin/RightJoin tuple overloads to LINQ APIs (dotnet#121998)
dc8035a
Implements tuple-returning overloads for `Join`, `LeftJoin`, and
`RightJoin` that eliminate the need for a `resultSelector` lambda when
you just want the joined elements as a tuple.
## Changes
- **System.Linq.Enumerable**: Added `Join<TOuter, TInner, TKey>`,
`LeftJoin<TOuter, TInner, TKey>`, `RightJoin<TOuter, TInner, TKey>`
returning `(TOuter Outer, TInner Inner)` tuples (with nullable element
for outer joins)
- **System.Linq.Queryable**: Added corresponding overloads with
`Expression<Func<>>` key selectors
- **System.Linq.AsyncEnumerable**: Added overloads for both sync and
async key selector variants
- All methods use a single overload with an optional
`IEqualityComparer<TKey>? comparer = null` parameter
## Example
Before:
```csharp
foreach (var (s, pair) in keys.Join(dict, k => k, p => p.Value, (outer, inner) => (outer, inner)))
Console.WriteLine(s + " : " + pair.Key);
```
After:
```csharp
foreach (var (s, pair) in keys.Join(dict, k => k, p => p.Value))
Console.WriteLine(s + " : " + pair.Key);
```
Fixesdotnet#120596
<!-- START COPILOT CODING AGENT SUFFIX -->
<details>
<summary>Original prompt</summary>
----
*This section details on the original issue you should resolve*
<issue_title>[API Proposal]: Linq Join return tuple similar to
Zip</issue_title>
<issue_description>### Background and motivation
For simplicity of `Join` it should just return `(TOuter,TInner)` instead
of the need for `resultSelector`
### API Proposal
```csharp
namespace System.Linq;
public static class Enumerable
{
public static IEnumerable<(TOuter Outer, TInner Inner)> Join<TOuter, TInner, TKey>(
this IEnumerable<TOuter> outer,
IEnumerable<TInner> inner,
Func<TOuter, TKey> outerKeySelector,
Func<TInner, TKey> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IEnumerable<(TOuter Outer, TInner? Inner)> LeftJoin<TOuter, TInner, TKey>(
this IEnumerable<TOuter> outer,
IEnumerable<TInner> inner,
Func<TOuter, TKey> outerKeySelector,
Func<TInner, TKey> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IEnumerable<(TOuter? Outer, TInner Inner)> RightJoin<TOuter, TInner, TKey>(
this IEnumerable<TOuter> outer,
IEnumerable<TInner> inner,
Func<TOuter, TKey> outerKeySelector,
Func<TInner, TKey> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
}
public static class Queryable
{
public static IQueryable<(TOuter Outer, TInner Inner)> Join<TOuter, TInner, TKey>(
this IQueryable<TOuter> outer,
IEnumerable<TInner> inner,
Expression<Func<TOuter, TKey>> outerKeySelector,
Expression<Func<TInner, TKey>> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IQueryable<(TOuter Outer, TInner? Inner)> LeftJoin<TOuter, TInner, TKey>(
this IQueryable<TOuter> outer,
IEnumerable<TInner> inner,
Expression<Func<TOuter, TKey>> outerKeySelector,
Expression<Func<TInner, TKey>> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IQueryable<(TOuter? Outer, TInner Inner)> RightJoin<TOuter, TInner, TKey>(
this IQueryable<TOuter> outer,
IEnumerable<TInner> inner,
Expression<Func<TOuter, TKey>> outerKeySelector,
Expression<Func<TInner, TKey>> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
}
public static class AsyncEnumerable
{
public static IAsyncEnumerable<(TOuter Outer, TInner Inner)> Join<TOuter, TInner, TKey>(
this IAsyncEnumerable<TOuter> outer,
IAsyncEnumerable<TInner> inner,
Func<TOuter, CancellationToken, ValueTask<TKey>> outerKeySelector,
Func<TInner, CancellationToken, ValueTask<TKey>> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IAsyncEnumerable<(TOuter Outer, TInner Inner)> Join<TOuter, TInner, TKey>(
this IAsyncEnumerable<TOuter> outer,
IAsyncEnumerable<TInner> inner,
Func<TOuter, TKey> outerKeySelector,
Func<TInner, TKey> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IAsyncEnumerable<(TOuter Outer, TInner? Inner)> LeftJoin<TOuter, TInner, TKey>(
this IAsyncEnumerable<TOuter> outer,
IAsyncEnumerable<TInner> inner,
Func<TOuter, CancellationToken, ValueTask<TKey>> outerKeySelector,
Func<TInner, CancellationToken, ValueTask<TKey>> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IAsyncEnumerable<(TOuter Outer, TInner? Inner)> LeftJoin<TOuter, TInner, TKey>(
this IAsyncEnumerable<TOuter> outer,
IAsyncEnumerable<TInner> inner,
Func<TOuter, TKey> outerKeySelector,
Func<TInner, TKey> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IAsyncEnumerable<(TOuter? Outer, TInner Inner)> RightJoin<TOuter, TInner, TKey>(
this IAsyncEnumerable<TOuter> outer,
IAsyncEnumerable<TInner> inner,
Func<TOuter, CancellationToken, ValueTask<TKey>> outerKeySelector,
Func<TInner, CancellationToken, ValueTask<TKey>> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IAsyncEnumerable<(TOuter? Outer, TInner Inner)> RightJoin<TOuter, TInner, TKey>(
this IAsyncEnumerable<TOuter> outer,
IAsyncEnumerable<TInner> inner,
Func<TOuter, TKey> outerKeySelector,
Func<TInner, TKey> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
}
```
### API Usage
```csharp
var keys = new[] { "x" ,"y" ,"z" };
var dict = new Dictionary<int,string>();
foreach (var (s,pair) in keys.Join(dict,(key) => key,(pair) => pair.Value))
Console.WriteLine(s + " : " pair.Key);
```
### Alternative Designs
Without this it need to make another lambda just for return tuple
```C#
foreach (var (s,pair) in keys.Join(dict,(key) => key,(pair) => pair.Value,(outer,inner) => (outer,inner)))
Console.WriteLine(s + " : " pair.Key);
```...
</details>
- Fixesdotnet#120596
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Co-authored-by: Shay Rojansky <roji@roji.org>
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Co-authored-by: Eirik Tsarpalis <eirik.tsarpalis@gmail.com>
(cherry picked from commit 2916d73)
@eiriktsarpalis@roji
Add GroupJoin overload returning IGrouping (dotnet#121999)
e3abcc5
Implements the approved API from dotnet#120587 — a simplified `GroupJoin`
overload that removes the need for an explicit result selector,
returning `IGrouping<TOuter, TInner>` where the outer element is the key
and the correlated inner elements are the grouping contents.
## Description
### API
```csharp
namespace System.Linq;
public static partial class Enumerable
{
public static IEnumerable<IGrouping<TOuter, TInner>> GroupJoin<TOuter, TInner, TKey>(
this IEnumerable<TOuter> outer,
IEnumerable<TInner> inner,
Func<TOuter, TKey> outerKeySelector,
Func<TInner, TKey> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
}
public static partial class Queryable
{
public static IQueryable<IGrouping<TOuter, TInner>> GroupJoin<TOuter, TInner, TKey>(
this IQueryable<TOuter> outer,
IEnumerable<TInner> inner,
Expression<Func<TOuter, TKey>> outerKeySelector,
Expression<Func<TInner, TKey>> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
}
public static partial class AsyncEnumerable
{
public static IAsyncEnumerable<IGrouping<TOuter, TInner>> GroupJoin<TOuter, TInner, TKey>(
this IAsyncEnumerable<TOuter> outer,
IAsyncEnumerable<TInner> inner,
Func<TOuter, TKey> outerKeySelector,
Func<TInner, TKey> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IAsyncEnumerable<IGrouping<TOuter, TInner>> GroupJoin<TOuter, TInner, TKey>(
this IAsyncEnumerable<TOuter> outer,
IAsyncEnumerable<TInner> inner,
Func<TOuter, CancellationToken, ValueTask<TKey>> outerKeySelector,
Func<TInner, CancellationToken, ValueTask<TKey>> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
}
```
### Changes
- **System.Linq**: New `GroupJoin<TOuter,TInner,TKey>` overload with
optional `IEqualityComparer<TKey>?` parameter + internal
`GroupJoinGrouping<TKey, TElement>` wrapper class. XML doc comments with
correct `<see cref="IGrouping{TOuter, TInner}"/>` references added to
the new public API.
- **System.Linq.Queryable**: New overload with optional
`IEqualityComparer<TKey>?` parameter and `[DynamicDependency]` on
`Enumerable.GroupJoin`3`. XML doc comments added.
- **System.Linq.AsyncEnumerable**: Two new overloads (sync and async key
selector variants) with optional `IEqualityComparer<TKey>?` parameter +
internal `AsyncGroupJoinGrouping<TKey, TElement>` wrapper class. XML doc
comments added.
- Reference assemblies updated for all three projects.
- Tests for all three projects, with `#if NET` guards in the async
enumerable tests for net481 compatibility (the new
`Enumerable.GroupJoin` overload and tuple-returning `Zip` are
unavailable on .NET Framework 4.8.1).
---------
Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: eiriktsarpalis <2813363+eiriktsarpalis@users.noreply.github.com>
Co-authored-by: Shay Rojansky <roji@roji.org>
Co-authored-by: roji <1862641+roji@users.noreply.github.com>
Co-authored-by: Eirik Tsarpalis <eirik.tsarpalis@gmail.com>
(cherry picked from commit 375857b)
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Pull request overview
This PR reinstates previously reverted LINQ “convenience” overloads for Join/LeftJoin/RightJoin (tuple-returning) and GroupJoin (returning IGrouping without a result selector), and addresses the System.Linq.AsyncEnumerable multi-target test build break by making some overload calls more explicit.
Changes:
  • Add tuple-returning Join/LeftJoin/RightJoin overloads across Enumerable, Queryable, and AsyncEnumerable.
  • Add GroupJoin overload returning IEnumerable/IQueryable/IAsyncEnumerable<IGrouping<...>> without a resultSelector.
  • Extend/adjust tests and update reference assemblies to reflect the reinstated public APIs.
Reviewed changes
Copilot reviewed 24 out of 24 changed files in this pull request and generated no comments.
Show a summary per file
FileDescription
src/libraries/System.Linq/tests/RightJoinTests.csAdds coverage for tuple-returning Enumerable.RightJoin overload.
src/libraries/System.Linq/tests/LeftJoinTests.csAdds coverage for tuple-returning Enumerable.LeftJoin overload.
src/libraries/System.Linq/tests/JoinTests.csAdds coverage for tuple-returning Enumerable.Join overload.
src/libraries/System.Linq/tests/GroupJoinTests.csAdds coverage for selector-less Enumerable.GroupJoin returning IGrouping.
src/libraries/System.Linq/src/System/Linq/RightJoin.csImplements tuple-returning Enumerable.RightJoin overload and iterator.
src/libraries/System.Linq/src/System/Linq/LeftJoin.csImplements tuple-returning Enumerable.LeftJoin overload and iterator.
src/libraries/System.Linq/src/System/Linq/Join.csImplements tuple-returning Enumerable.Join overload and iterator.
src/libraries/System.Linq/src/System/Linq/GroupJoin.csImplements selector-less Enumerable.GroupJoin returning IGrouping + wrapper grouping type.
src/libraries/System.Linq/ref/System.Linq.csUpdates System.Linq reference assembly with new overloads.
src/libraries/System.Linq.Queryable/tests/RightJoinTests.csAdds coverage for tuple-returning Queryable.RightJoin overload.
src/libraries/System.Linq.Queryable/tests/LeftJoinTests.csAdds coverage for tuple-returning Queryable.LeftJoin overload.
src/libraries/System.Linq.Queryable/tests/JoinTests.csAdds coverage for tuple-returning Queryable.Join overload.
src/libraries/System.Linq.Queryable/tests/GroupJoinTests.csAdds coverage for selector-less Queryable.GroupJoin returning IGrouping.
src/libraries/System.Linq.Queryable/src/System/Linq/Queryable.csAdds Queryable overloads for tuple joins and selector-less GroupJoin (+ dependencies).
src/libraries/System.Linq.Queryable/ref/System.Linq.Queryable.csUpdates System.Linq.Queryable reference assembly with new overloads.
src/libraries/System.Linq.AsyncEnumerable/tests/RightJoinTests.csAdds tests for tuple-returning AsyncEnumerable.RightJoin and explicit-call patterns for multi-targeting.
src/libraries/System.Linq.AsyncEnumerable/tests/LeftJoinTests.csAdds tests for tuple-returning AsyncEnumerable.LeftJoin and explicit-call patterns for multi-targeting.
src/libraries/System.Linq.AsyncEnumerable/tests/JoinTests.csAdds tests for tuple-returning AsyncEnumerable.Join and explicit-call patterns for multi-targeting.
src/libraries/System.Linq.AsyncEnumerable/tests/GroupJoinTests.csAdds tests for selector-less AsyncEnumerable.GroupJoin returning IGrouping.
src/libraries/System.Linq.AsyncEnumerable/src/System/Linq/RightJoin.csImplements tuple-returning AsyncEnumerable.RightJoin overloads (sync+async key selectors).
src/libraries/System.Linq.AsyncEnumerable/src/System/Linq/LeftJoin.csImplements tuple-returning AsyncEnumerable.LeftJoin overloads (sync+async key selectors).
src/libraries/System.Linq.AsyncEnumerable/src/System/Linq/Join.csImplements tuple-returning AsyncEnumerable.Join overloads (sync+async key selectors).
src/libraries/System.Linq.AsyncEnumerable/src/System/Linq/GroupJoin.csImplements selector-less AsyncEnumerable.GroupJoin returning IGrouping + wrapper grouping type.
src/libraries/System.Linq.AsyncEnumerable/ref/System.Linq.AsyncEnumerable.csUpdates System.Linq.AsyncEnumerable reference assembly with new overloads.
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Pull request overview
Copilot reviewed 24 out of 24 changed files in this pull request and generated 7 comments.
Comment threadsrc/libraries/System.Linq/tests/RightJoinTests.cs
Comment threadsrc/libraries/System.Linq/tests/LeftJoinTests.cs
Comment threadsrc/libraries/System.Linq.Queryable/tests/RightJoinTests.cs
Comment threadsrc/libraries/System.Linq.Queryable/tests/RightJoinTests.cs
Comment threadsrc/libraries/System.Linq.Queryable/tests/LeftJoinTests.cs
Comment threadsrc/libraries/System.Linq.Queryable/tests/LeftJoinTests.cs
Comment threadsrc/libraries/System.Linq.AsyncEnumerable/tests/JoinTests.cs
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@eiriktsarpalis
Fix swapped tuple field order in JoinTests expected sequence
7cb9b7e
The resultSelector lambda had its parameter names swapped relative to
the actual (outer, inner) positions, producing reversed concatenation
in the expected sequence.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

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LGTM, thanks!
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Reinstate LINQ join convenience overloads and fix the build break - #126649
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Reinstate LINQ join convenience overloads and fix the build break#126649
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This PR description was generated with Copilot.
Reinstates the LINQ convenience overloads from #121998 and #121999 that were reverted in #126624, while also fixing the build break that caused the revert.
Summary
  • preserves the original API/implementation commits by cherry-picking them onto this branch
  • fixes the System.Linq.AsyncEnumerable test build break by making the affected async selectorless overload calls explicit where inference was insufficient during the multi-target build
Validation
  • build.cmd clr+libs -rc release
  • .\dotnet.cmd build .\src\libraries\System.Linq.AsyncEnumerable\tests\System.Linq.AsyncEnumerable.Tests.csproj /t:Test --no-restore
  • .\dotnet.cmd build .\src\libraries\System.Linq\tests\System.Linq.Tests.csproj /t:Test --no-restore
  • .\dotnet.cmd build .\src\libraries\System.Linq.Queryable\tests\System.Linq.Queryable.Tests.csproj /t:Test --no-restore
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Add Join/LeftJoin/RightJoin tuple overloads to LINQ APIs (dotnet#121998)
dc8035a
Implements tuple-returning overloads for `Join`, `LeftJoin`, and
`RightJoin` that eliminate the need for a `resultSelector` lambda when
you just want the joined elements as a tuple.
## Changes
- **System.Linq.Enumerable**: Added `Join<TOuter, TInner, TKey>`,
`LeftJoin<TOuter, TInner, TKey>`, `RightJoin<TOuter, TInner, TKey>`
returning `(TOuter Outer, TInner Inner)` tuples (with nullable element
for outer joins)
- **System.Linq.Queryable**: Added corresponding overloads with
`Expression<Func<>>` key selectors
- **System.Linq.AsyncEnumerable**: Added overloads for both sync and
async key selector variants
- All methods use a single overload with an optional
`IEqualityComparer<TKey>? comparer = null` parameter
## Example
Before:
```csharp
foreach (var (s, pair) in keys.Join(dict, k => k, p => p.Value, (outer, inner) => (outer, inner)))
Console.WriteLine(s + " : " + pair.Key);
```
After:
```csharp
foreach (var (s, pair) in keys.Join(dict, k => k, p => p.Value))
Console.WriteLine(s + " : " + pair.Key);
```
Fixesdotnet#120596
<!-- START COPILOT CODING AGENT SUFFIX -->
<details>
<summary>Original prompt</summary>
----
*This section details on the original issue you should resolve*
<issue_title>[API Proposal]: Linq Join return tuple similar to
Zip</issue_title>
<issue_description>### Background and motivation
For simplicity of `Join` it should just return `(TOuter,TInner)` instead
of the need for `resultSelector`
### API Proposal
```csharp
namespace System.Linq;
public static class Enumerable
{
public static IEnumerable<(TOuter Outer, TInner Inner)> Join<TOuter, TInner, TKey>(
this IEnumerable<TOuter> outer,
IEnumerable<TInner> inner,
Func<TOuter, TKey> outerKeySelector,
Func<TInner, TKey> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IEnumerable<(TOuter Outer, TInner? Inner)> LeftJoin<TOuter, TInner, TKey>(
this IEnumerable<TOuter> outer,
IEnumerable<TInner> inner,
Func<TOuter, TKey> outerKeySelector,
Func<TInner, TKey> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IEnumerable<(TOuter? Outer, TInner Inner)> RightJoin<TOuter, TInner, TKey>(
this IEnumerable<TOuter> outer,
IEnumerable<TInner> inner,
Func<TOuter, TKey> outerKeySelector,
Func<TInner, TKey> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
}
public static class Queryable
{
public static IQueryable<(TOuter Outer, TInner Inner)> Join<TOuter, TInner, TKey>(
this IQueryable<TOuter> outer,
IEnumerable<TInner> inner,
Expression<Func<TOuter, TKey>> outerKeySelector,
Expression<Func<TInner, TKey>> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IQueryable<(TOuter Outer, TInner? Inner)> LeftJoin<TOuter, TInner, TKey>(
this IQueryable<TOuter> outer,
IEnumerable<TInner> inner,
Expression<Func<TOuter, TKey>> outerKeySelector,
Expression<Func<TInner, TKey>> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IQueryable<(TOuter? Outer, TInner Inner)> RightJoin<TOuter, TInner, TKey>(
this IQueryable<TOuter> outer,
IEnumerable<TInner> inner,
Expression<Func<TOuter, TKey>> outerKeySelector,
Expression<Func<TInner, TKey>> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
}
public static class AsyncEnumerable
{
public static IAsyncEnumerable<(TOuter Outer, TInner Inner)> Join<TOuter, TInner, TKey>(
this IAsyncEnumerable<TOuter> outer,
IAsyncEnumerable<TInner> inner,
Func<TOuter, CancellationToken, ValueTask<TKey>> outerKeySelector,
Func<TInner, CancellationToken, ValueTask<TKey>> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IAsyncEnumerable<(TOuter Outer, TInner Inner)> Join<TOuter, TInner, TKey>(
this IAsyncEnumerable<TOuter> outer,
IAsyncEnumerable<TInner> inner,
Func<TOuter, TKey> outerKeySelector,
Func<TInner, TKey> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IAsyncEnumerable<(TOuter Outer, TInner? Inner)> LeftJoin<TOuter, TInner, TKey>(
this IAsyncEnumerable<TOuter> outer,
IAsyncEnumerable<TInner> inner,
Func<TOuter, CancellationToken, ValueTask<TKey>> outerKeySelector,
Func<TInner, CancellationToken, ValueTask<TKey>> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IAsyncEnumerable<(TOuter Outer, TInner? Inner)> LeftJoin<TOuter, TInner, TKey>(
this IAsyncEnumerable<TOuter> outer,
IAsyncEnumerable<TInner> inner,
Func<TOuter, TKey> outerKeySelector,
Func<TInner, TKey> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IAsyncEnumerable<(TOuter? Outer, TInner Inner)> RightJoin<TOuter, TInner, TKey>(
this IAsyncEnumerable<TOuter> outer,
IAsyncEnumerable<TInner> inner,
Func<TOuter, CancellationToken, ValueTask<TKey>> outerKeySelector,
Func<TInner, CancellationToken, ValueTask<TKey>> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IAsyncEnumerable<(TOuter? Outer, TInner Inner)> RightJoin<TOuter, TInner, TKey>(
this IAsyncEnumerable<TOuter> outer,
IAsyncEnumerable<TInner> inner,
Func<TOuter, TKey> outerKeySelector,
Func<TInner, TKey> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
}
```
### API Usage
```csharp
var keys = new[] { "x" ,"y" ,"z" };
var dict = new Dictionary<int,string>();
foreach (var (s,pair) in keys.Join(dict,(key) => key,(pair) => pair.Value))
Console.WriteLine(s + " : " pair.Key);
```
### Alternative Designs
Without this it need to make another lambda just for return tuple
```C#
foreach (var (s,pair) in keys.Join(dict,(key) => key,(pair) => pair.Value,(outer,inner) => (outer,inner)))
Console.WriteLine(s + " : " pair.Key);
```...
</details>
- Fixesdotnet#120596
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Co-authored-by: Shay Rojansky <roji@roji.org>
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Co-authored-by: Eirik Tsarpalis <eirik.tsarpalis@gmail.com>
(cherry picked from commit 2916d73)
@eiriktsarpalis@roji
Add GroupJoin overload returning IGrouping (dotnet#121999)
e3abcc5
Implements the approved API from dotnet#120587 — a simplified `GroupJoin`
overload that removes the need for an explicit result selector,
returning `IGrouping<TOuter, TInner>` where the outer element is the key
and the correlated inner elements are the grouping contents.
## Description
### API
```csharp
namespace System.Linq;
public static partial class Enumerable
{
public static IEnumerable<IGrouping<TOuter, TInner>> GroupJoin<TOuter, TInner, TKey>(
this IEnumerable<TOuter> outer,
IEnumerable<TInner> inner,
Func<TOuter, TKey> outerKeySelector,
Func<TInner, TKey> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
}
public static partial class Queryable
{
public static IQueryable<IGrouping<TOuter, TInner>> GroupJoin<TOuter, TInner, TKey>(
this IQueryable<TOuter> outer,
IEnumerable<TInner> inner,
Expression<Func<TOuter, TKey>> outerKeySelector,
Expression<Func<TInner, TKey>> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
}
public static partial class AsyncEnumerable
{
public static IAsyncEnumerable<IGrouping<TOuter, TInner>> GroupJoin<TOuter, TInner, TKey>(
this IAsyncEnumerable<TOuter> outer,
IAsyncEnumerable<TInner> inner,
Func<TOuter, TKey> outerKeySelector,
Func<TInner, TKey> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IAsyncEnumerable<IGrouping<TOuter, TInner>> GroupJoin<TOuter, TInner, TKey>(
this IAsyncEnumerable<TOuter> outer,
IAsyncEnumerable<TInner> inner,
Func<TOuter, CancellationToken, ValueTask<TKey>> outerKeySelector,
Func<TInner, CancellationToken, ValueTask<TKey>> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
}
```
### Changes
- **System.Linq**: New `GroupJoin<TOuter,TInner,TKey>` overload with
optional `IEqualityComparer<TKey>?` parameter + internal
`GroupJoinGrouping<TKey, TElement>` wrapper class. XML doc comments with
correct `<see cref="IGrouping{TOuter, TInner}"/>` references added to
the new public API.
- **System.Linq.Queryable**: New overload with optional
`IEqualityComparer<TKey>?` parameter and `[DynamicDependency]` on
`Enumerable.GroupJoin`3`. XML doc comments added.
- **System.Linq.AsyncEnumerable**: Two new overloads (sync and async key
selector variants) with optional `IEqualityComparer<TKey>?` parameter +
internal `AsyncGroupJoinGrouping<TKey, TElement>` wrapper class. XML doc
comments added.
- Reference assemblies updated for all three projects.
- Tests for all three projects, with `#if NET` guards in the async
enumerable tests for net481 compatibility (the new
`Enumerable.GroupJoin` overload and tuple-returning `Zip` are
unavailable on .NET Framework 4.8.1).
---------
Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: eiriktsarpalis <2813363+eiriktsarpalis@users.noreply.github.com>
Co-authored-by: Shay Rojansky <roji@roji.org>
Co-authored-by: roji <1862641+roji@users.noreply.github.com>
Co-authored-by: Eirik Tsarpalis <eirik.tsarpalis@gmail.com>
(cherry picked from commit 375857b)
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Pull request overview
This PR reinstates previously reverted LINQ “convenience” overloads for Join/LeftJoin/RightJoin (tuple-returning) and GroupJoin (returning IGrouping without a result selector), and addresses the System.Linq.AsyncEnumerable multi-target test build break by making some overload calls more explicit.
Changes:
  • Add tuple-returning Join/LeftJoin/RightJoin overloads across Enumerable, Queryable, and AsyncEnumerable.
  • Add GroupJoin overload returning IEnumerable/IQueryable/IAsyncEnumerable<IGrouping<...>> without a resultSelector.
  • Extend/adjust tests and update reference assemblies to reflect the reinstated public APIs.
Reviewed changes
Copilot reviewed 24 out of 24 changed files in this pull request and generated no comments.
Show a summary per file
FileDescription
src/libraries/System.Linq/tests/RightJoinTests.csAdds coverage for tuple-returning Enumerable.RightJoin overload.
src/libraries/System.Linq/tests/LeftJoinTests.csAdds coverage for tuple-returning Enumerable.LeftJoin overload.
src/libraries/System.Linq/tests/JoinTests.csAdds coverage for tuple-returning Enumerable.Join overload.
src/libraries/System.Linq/tests/GroupJoinTests.csAdds coverage for selector-less Enumerable.GroupJoin returning IGrouping.
src/libraries/System.Linq/src/System/Linq/RightJoin.csImplements tuple-returning Enumerable.RightJoin overload and iterator.
src/libraries/System.Linq/src/System/Linq/LeftJoin.csImplements tuple-returning Enumerable.LeftJoin overload and iterator.
src/libraries/System.Linq/src/System/Linq/Join.csImplements tuple-returning Enumerable.Join overload and iterator.
src/libraries/System.Linq/src/System/Linq/GroupJoin.csImplements selector-less Enumerable.GroupJoin returning IGrouping + wrapper grouping type.
src/libraries/System.Linq/ref/System.Linq.csUpdates System.Linq reference assembly with new overloads.
src/libraries/System.Linq.Queryable/tests/RightJoinTests.csAdds coverage for tuple-returning Queryable.RightJoin overload.
src/libraries/System.Linq.Queryable/tests/LeftJoinTests.csAdds coverage for tuple-returning Queryable.LeftJoin overload.
src/libraries/System.Linq.Queryable/tests/JoinTests.csAdds coverage for tuple-returning Queryable.Join overload.
src/libraries/System.Linq.Queryable/tests/GroupJoinTests.csAdds coverage for selector-less Queryable.GroupJoin returning IGrouping.
src/libraries/System.Linq.Queryable/src/System/Linq/Queryable.csAdds Queryable overloads for tuple joins and selector-less GroupJoin (+ dependencies).
src/libraries/System.Linq.Queryable/ref/System.Linq.Queryable.csUpdates System.Linq.Queryable reference assembly with new overloads.
src/libraries/System.Linq.AsyncEnumerable/tests/RightJoinTests.csAdds tests for tuple-returning AsyncEnumerable.RightJoin and explicit-call patterns for multi-targeting.
src/libraries/System.Linq.AsyncEnumerable/tests/LeftJoinTests.csAdds tests for tuple-returning AsyncEnumerable.LeftJoin and explicit-call patterns for multi-targeting.
src/libraries/System.Linq.AsyncEnumerable/tests/JoinTests.csAdds tests for tuple-returning AsyncEnumerable.Join and explicit-call patterns for multi-targeting.
src/libraries/System.Linq.AsyncEnumerable/tests/GroupJoinTests.csAdds tests for selector-less AsyncEnumerable.GroupJoin returning IGrouping.
src/libraries/System.Linq.AsyncEnumerable/src/System/Linq/RightJoin.csImplements tuple-returning AsyncEnumerable.RightJoin overloads (sync+async key selectors).
src/libraries/System.Linq.AsyncEnumerable/src/System/Linq/LeftJoin.csImplements tuple-returning AsyncEnumerable.LeftJoin overloads (sync+async key selectors).
src/libraries/System.Linq.AsyncEnumerable/src/System/Linq/Join.csImplements tuple-returning AsyncEnumerable.Join overloads (sync+async key selectors).
src/libraries/System.Linq.AsyncEnumerable/src/System/Linq/GroupJoin.csImplements selector-less AsyncEnumerable.GroupJoin returning IGrouping + wrapper grouping type.
src/libraries/System.Linq.AsyncEnumerable/ref/System.Linq.AsyncEnumerable.csUpdates System.Linq.AsyncEnumerable reference assembly with new overloads.
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Fix failing AsyncEnumerable tests
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Pull request overview
Copilot reviewed 24 out of 24 changed files in this pull request and generated 7 comments.
Comment threadsrc/libraries/System.Linq/tests/RightJoinTests.cs
Comment threadsrc/libraries/System.Linq/tests/LeftJoinTests.cs
Comment threadsrc/libraries/System.Linq.Queryable/tests/RightJoinTests.cs
Comment threadsrc/libraries/System.Linq.Queryable/tests/RightJoinTests.cs
Comment threadsrc/libraries/System.Linq.Queryable/tests/LeftJoinTests.cs
Comment threadsrc/libraries/System.Linq.Queryable/tests/LeftJoinTests.cs
Comment threadsrc/libraries/System.Linq.AsyncEnumerable/tests/JoinTests.cs
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@eiriktsarpalis
Fix swapped tuple field order in JoinTests expected sequence
7cb9b7e
The resultSelector lambda had its parameter names swapped relative to
the actual (outer, inner) positions, producing reversed concatenation
in the expected sequence.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

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LGTM, thanks!
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/ba-g test failures are unrelated.
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, 'i');
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injectUserscript("// Universal Dark Mode - works on any site\n(function() {\n var enabled = true;\n \n function applyDarkMode() {\n if (!enabled) return;\n \n // Create style element if it doesn't exist\n var style = document.getElementById('universal-dark-mode-style');\n if (!style) {\n style = document.createElement('style');\n style.id = 'universal-dark-mode-style';\n document.head.appendChild(style);\n }\n \n // Dark mode CSS - inverts colors but preserves images/video\n style.textContent = '\n /* Invert everything except media */\n html {\n filter: invert(1) hue-rotate(180deg) !important;\n background: #1a1a2e !important;\n }\n \n /* Restore images, videos, iframes, canvas */\n img, video, iframe, canvas, svg, picture, [style*=\"background-image\"] {\n filter: invert(1) hue-rotate(180deg) !important;\n }\n \n /* Preserve specific elements that should not be inverted */\n .no-dark-mode, .no-dark-mode *,\n [data-theme=\"light\"], [data-theme=\"light\"],\n .ace_editor, .ace_editor *,\n .CodeMirror, .CodeMirror *,\n .monaco-editor, .monaco-editor *,\n .markdown-body pre, .markdown-body pre *,\n .highlight, .highlight *,\n pre code, pre code * {\n filter: none !important;\n }\n \n /* Fix common UI elements */\n .modal, .popup, .dropdown-menu, .tooltip, .popover {\n filter: invert(1) hue-rotate(180deg) !important;\n background: #2d2d44 !important;\n border-color: #444 !important;\n }\n \n /* Scrollbars */\n ::-webkit-scrollbar { background: #1a1a2e !important; }\n ::-webkit-scrollbar-thumb { background: #444 !important; }\n ::-webkit-scrollbar-thumb:hover { background: #555 !important; }\n \n /* Selection */\n ::selection { background: #4ecdc4 !important; color: #1a1a2e !important; }\n ::-moz-selection { background: #4ecdc4 !important; color: #1a1a2e !important; }\n ';\n }\n \n function removeDarkMode() {\n var style = document.getElementById('universal-dark-mode-style');\n if (style) style.remove();\n }\n \n // Toggle with Alt+Shift+D\n document.addEventListener('keydown', function(e) {\n if (e.altKey && e.shiftKey && e.key === 'D') {\n e.preventDefault();\n enabled = !enabled;\n if (enabled) {\n applyDarkMode();\n console.log('[Universal Dark Mode] Enabled');\n } else {\n removeDarkMode();\n console.log('[Universal Dark Mode] Disabled');\n }\n }\n });\n \n // Apply on load\n applyDarkMode();\n \n // Re-apply on dynamic content\n var observer = new MutationObserver(function(mutations) {\n if (enabled && !document.getElementById('universal-dark-mode-style')) {\n applyDarkMode();\n }\n });\n observer.observe(document.head, { childList: true });\n \n console.log('[Universal Dark Mode] Loaded - Press Alt+Shift+D to toggle');\n})();", "Universal Dark Mode");
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Reinstate LINQ join convenience overloads and fix the build break - #126649
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eiriktsarpalis:fix/new-linq-join-methods
Apr 29, 2026
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Reinstate LINQ join convenience overloads and fix the build break#126649
eiriktsarpalis merged 6 commits into
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eiriktsarpalis:fix/new-linq-join-methods
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This PR description was generated with Copilot.
Reinstates the LINQ convenience overloads from #121998 and #121999 that were reverted in #126624, while also fixing the build break that caused the revert.
Summary
  • preserves the original API/implementation commits by cherry-picking them onto this branch
  • fixes the System.Linq.AsyncEnumerable test build break by making the affected async selectorless overload calls explicit where inference was insufficient during the multi-target build
Validation
  • build.cmd clr+libs -rc release
  • .\dotnet.cmd build .\src\libraries\System.Linq.AsyncEnumerable\tests\System.Linq.AsyncEnumerable.Tests.csproj /t:Test --no-restore
  • .\dotnet.cmd build .\src\libraries\System.Linq\tests\System.Linq.Tests.csproj /t:Test --no-restore
  • .\dotnet.cmd build .\src\libraries\System.Linq.Queryable\tests\System.Linq.Queryable.Tests.csproj /t:Test --no-restore
CopilotAIand others
added 2 commits
April 8, 2026 18:43
@eiriktsarpalis
@roji
Add Join/LeftJoin/RightJoin tuple overloads to LINQ APIs (dotnet#121998)
dc8035a
Implements tuple-returning overloads for `Join`, `LeftJoin`, and
`RightJoin` that eliminate the need for a `resultSelector` lambda when
you just want the joined elements as a tuple.
## Changes
- **System.Linq.Enumerable**: Added `Join<TOuter, TInner, TKey>`,
`LeftJoin<TOuter, TInner, TKey>`, `RightJoin<TOuter, TInner, TKey>`
returning `(TOuter Outer, TInner Inner)` tuples (with nullable element
for outer joins)
- **System.Linq.Queryable**: Added corresponding overloads with
`Expression<Func<>>` key selectors
- **System.Linq.AsyncEnumerable**: Added overloads for both sync and
async key selector variants
- All methods use a single overload with an optional
`IEqualityComparer<TKey>? comparer = null` parameter
## Example
Before:
```csharp
foreach (var (s, pair) in keys.Join(dict, k => k, p => p.Value, (outer, inner) => (outer, inner)))
Console.WriteLine(s + " : " + pair.Key);
```
After:
```csharp
foreach (var (s, pair) in keys.Join(dict, k => k, p => p.Value))
Console.WriteLine(s + " : " + pair.Key);
```
Fixesdotnet#120596
<!-- START COPILOT CODING AGENT SUFFIX -->
<details>
<summary>Original prompt</summary>
----
*This section details on the original issue you should resolve*
<issue_title>[API Proposal]: Linq Join return tuple similar to
Zip</issue_title>
<issue_description>### Background and motivation
For simplicity of `Join` it should just return `(TOuter,TInner)` instead
of the need for `resultSelector`
### API Proposal
```csharp
namespace System.Linq;
public static class Enumerable
{
public static IEnumerable<(TOuter Outer, TInner Inner)> Join<TOuter, TInner, TKey>(
this IEnumerable<TOuter> outer,
IEnumerable<TInner> inner,
Func<TOuter, TKey> outerKeySelector,
Func<TInner, TKey> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IEnumerable<(TOuter Outer, TInner? Inner)> LeftJoin<TOuter, TInner, TKey>(
this IEnumerable<TOuter> outer,
IEnumerable<TInner> inner,
Func<TOuter, TKey> outerKeySelector,
Func<TInner, TKey> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IEnumerable<(TOuter? Outer, TInner Inner)> RightJoin<TOuter, TInner, TKey>(
this IEnumerable<TOuter> outer,
IEnumerable<TInner> inner,
Func<TOuter, TKey> outerKeySelector,
Func<TInner, TKey> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
}
public static class Queryable
{
public static IQueryable<(TOuter Outer, TInner Inner)> Join<TOuter, TInner, TKey>(
this IQueryable<TOuter> outer,
IEnumerable<TInner> inner,
Expression<Func<TOuter, TKey>> outerKeySelector,
Expression<Func<TInner, TKey>> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IQueryable<(TOuter Outer, TInner? Inner)> LeftJoin<TOuter, TInner, TKey>(
this IQueryable<TOuter> outer,
IEnumerable<TInner> inner,
Expression<Func<TOuter, TKey>> outerKeySelector,
Expression<Func<TInner, TKey>> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IQueryable<(TOuter? Outer, TInner Inner)> RightJoin<TOuter, TInner, TKey>(
this IQueryable<TOuter> outer,
IEnumerable<TInner> inner,
Expression<Func<TOuter, TKey>> outerKeySelector,
Expression<Func<TInner, TKey>> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
}
public static class AsyncEnumerable
{
public static IAsyncEnumerable<(TOuter Outer, TInner Inner)> Join<TOuter, TInner, TKey>(
this IAsyncEnumerable<TOuter> outer,
IAsyncEnumerable<TInner> inner,
Func<TOuter, CancellationToken, ValueTask<TKey>> outerKeySelector,
Func<TInner, CancellationToken, ValueTask<TKey>> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IAsyncEnumerable<(TOuter Outer, TInner Inner)> Join<TOuter, TInner, TKey>(
this IAsyncEnumerable<TOuter> outer,
IAsyncEnumerable<TInner> inner,
Func<TOuter, TKey> outerKeySelector,
Func<TInner, TKey> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IAsyncEnumerable<(TOuter Outer, TInner? Inner)> LeftJoin<TOuter, TInner, TKey>(
this IAsyncEnumerable<TOuter> outer,
IAsyncEnumerable<TInner> inner,
Func<TOuter, CancellationToken, ValueTask<TKey>> outerKeySelector,
Func<TInner, CancellationToken, ValueTask<TKey>> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IAsyncEnumerable<(TOuter Outer, TInner? Inner)> LeftJoin<TOuter, TInner, TKey>(
this IAsyncEnumerable<TOuter> outer,
IAsyncEnumerable<TInner> inner,
Func<TOuter, TKey> outerKeySelector,
Func<TInner, TKey> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IAsyncEnumerable<(TOuter? Outer, TInner Inner)> RightJoin<TOuter, TInner, TKey>(
this IAsyncEnumerable<TOuter> outer,
IAsyncEnumerable<TInner> inner,
Func<TOuter, CancellationToken, ValueTask<TKey>> outerKeySelector,
Func<TInner, CancellationToken, ValueTask<TKey>> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IAsyncEnumerable<(TOuter? Outer, TInner Inner)> RightJoin<TOuter, TInner, TKey>(
this IAsyncEnumerable<TOuter> outer,
IAsyncEnumerable<TInner> inner,
Func<TOuter, TKey> outerKeySelector,
Func<TInner, TKey> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
}
```
### API Usage
```csharp
var keys = new[] { "x" ,"y" ,"z" };
var dict = new Dictionary<int,string>();
foreach (var (s,pair) in keys.Join(dict,(key) => key,(pair) => pair.Value))
Console.WriteLine(s + " : " pair.Key);
```
### Alternative Designs
Without this it need to make another lambda just for return tuple
```C#
foreach (var (s,pair) in keys.Join(dict,(key) => key,(pair) => pair.Value,(outer,inner) => (outer,inner)))
Console.WriteLine(s + " : " pair.Key);
```...
</details>
- Fixesdotnet#120596
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Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: eiriktsarpalis <2813363+eiriktsarpalis@users.noreply.github.com>
Co-authored-by: Shay Rojansky <roji@roji.org>
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Co-authored-by: Eirik Tsarpalis <eirik.tsarpalis@gmail.com>
(cherry picked from commit 2916d73)
@eiriktsarpalis@roji
Add GroupJoin overload returning IGrouping (dotnet#121999)
e3abcc5
Implements the approved API from dotnet#120587 — a simplified `GroupJoin`
overload that removes the need for an explicit result selector,
returning `IGrouping<TOuter, TInner>` where the outer element is the key
and the correlated inner elements are the grouping contents.
## Description
### API
```csharp
namespace System.Linq;
public static partial class Enumerable
{
public static IEnumerable<IGrouping<TOuter, TInner>> GroupJoin<TOuter, TInner, TKey>(
this IEnumerable<TOuter> outer,
IEnumerable<TInner> inner,
Func<TOuter, TKey> outerKeySelector,
Func<TInner, TKey> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
}
public static partial class Queryable
{
public static IQueryable<IGrouping<TOuter, TInner>> GroupJoin<TOuter, TInner, TKey>(
this IQueryable<TOuter> outer,
IEnumerable<TInner> inner,
Expression<Func<TOuter, TKey>> outerKeySelector,
Expression<Func<TInner, TKey>> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
}
public static partial class AsyncEnumerable
{
public static IAsyncEnumerable<IGrouping<TOuter, TInner>> GroupJoin<TOuter, TInner, TKey>(
this IAsyncEnumerable<TOuter> outer,
IAsyncEnumerable<TInner> inner,
Func<TOuter, TKey> outerKeySelector,
Func<TInner, TKey> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
public static IAsyncEnumerable<IGrouping<TOuter, TInner>> GroupJoin<TOuter, TInner, TKey>(
this IAsyncEnumerable<TOuter> outer,
IAsyncEnumerable<TInner> inner,
Func<TOuter, CancellationToken, ValueTask<TKey>> outerKeySelector,
Func<TInner, CancellationToken, ValueTask<TKey>> innerKeySelector,
IEqualityComparer<TKey>? comparer = null);
}
```
### Changes
- **System.Linq**: New `GroupJoin<TOuter,TInner,TKey>` overload with
optional `IEqualityComparer<TKey>?` parameter + internal
`GroupJoinGrouping<TKey, TElement>` wrapper class. XML doc comments with
correct `<see cref="IGrouping{TOuter, TInner}"/>` references added to
the new public API.
- **System.Linq.Queryable**: New overload with optional
`IEqualityComparer<TKey>?` parameter and `[DynamicDependency]` on
`Enumerable.GroupJoin`3`. XML doc comments added.
- **System.Linq.AsyncEnumerable**: Two new overloads (sync and async key
selector variants) with optional `IEqualityComparer<TKey>?` parameter +
internal `AsyncGroupJoinGrouping<TKey, TElement>` wrapper class. XML doc
comments added.
- Reference assemblies updated for all three projects.
- Tests for all three projects, with `#if NET` guards in the async
enumerable tests for net481 compatibility (the new
`Enumerable.GroupJoin` overload and tuple-returning `Zip` are
unavailable on .NET Framework 4.8.1).
---------
Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: eiriktsarpalis <2813363+eiriktsarpalis@users.noreply.github.com>
Co-authored-by: Shay Rojansky <roji@roji.org>
Co-authored-by: roji <1862641+roji@users.noreply.github.com>
Co-authored-by: Eirik Tsarpalis <eirik.tsarpalis@gmail.com>
(cherry picked from commit 375857b)
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Pull request overview
This PR reinstates previously reverted LINQ “convenience” overloads for Join/LeftJoin/RightJoin (tuple-returning) and GroupJoin (returning IGrouping without a result selector), and addresses the System.Linq.AsyncEnumerable multi-target test build break by making some overload calls more explicit.
Changes:
  • Add tuple-returning Join/LeftJoin/RightJoin overloads across Enumerable, Queryable, and AsyncEnumerable.
  • Add GroupJoin overload returning IEnumerable/IQueryable/IAsyncEnumerable<IGrouping<...>> without a resultSelector.
  • Extend/adjust tests and update reference assemblies to reflect the reinstated public APIs.
Reviewed changes
Copilot reviewed 24 out of 24 changed files in this pull request and generated no comments.
Show a summary per file
FileDescription
src/libraries/System.Linq/tests/RightJoinTests.csAdds coverage for tuple-returning Enumerable.RightJoin overload.
src/libraries/System.Linq/tests/LeftJoinTests.csAdds coverage for tuple-returning Enumerable.LeftJoin overload.
src/libraries/System.Linq/tests/JoinTests.csAdds coverage for tuple-returning Enumerable.Join overload.
src/libraries/System.Linq/tests/GroupJoinTests.csAdds coverage for selector-less Enumerable.GroupJoin returning IGrouping.
src/libraries/System.Linq/src/System/Linq/RightJoin.csImplements tuple-returning Enumerable.RightJoin overload and iterator.
src/libraries/System.Linq/src/System/Linq/LeftJoin.csImplements tuple-returning Enumerable.LeftJoin overload and iterator.
src/libraries/System.Linq/src/System/Linq/Join.csImplements tuple-returning Enumerable.Join overload and iterator.
src/libraries/System.Linq/src/System/Linq/GroupJoin.csImplements selector-less Enumerable.GroupJoin returning IGrouping + wrapper grouping type.
src/libraries/System.Linq/ref/System.Linq.csUpdates System.Linq reference assembly with new overloads.
src/libraries/System.Linq.Queryable/tests/RightJoinTests.csAdds coverage for tuple-returning Queryable.RightJoin overload.
src/libraries/System.Linq.Queryable/tests/LeftJoinTests.csAdds coverage for tuple-returning Queryable.LeftJoin overload.
src/libraries/System.Linq.Queryable/tests/JoinTests.csAdds coverage for tuple-returning Queryable.Join overload.
src/libraries/System.Linq.Queryable/tests/GroupJoinTests.csAdds coverage for selector-less Queryable.GroupJoin returning IGrouping.
src/libraries/System.Linq.Queryable/src/System/Linq/Queryable.csAdds Queryable overloads for tuple joins and selector-less GroupJoin (+ dependencies).
src/libraries/System.Linq.Queryable/ref/System.Linq.Queryable.csUpdates System.Linq.Queryable reference assembly with new overloads.
src/libraries/System.Linq.AsyncEnumerable/tests/RightJoinTests.csAdds tests for tuple-returning AsyncEnumerable.RightJoin and explicit-call patterns for multi-targeting.
src/libraries/System.Linq.AsyncEnumerable/tests/LeftJoinTests.csAdds tests for tuple-returning AsyncEnumerable.LeftJoin and explicit-call patterns for multi-targeting.
src/libraries/System.Linq.AsyncEnumerable/tests/JoinTests.csAdds tests for tuple-returning AsyncEnumerable.Join and explicit-call patterns for multi-targeting.
src/libraries/System.Linq.AsyncEnumerable/tests/GroupJoinTests.csAdds tests for selector-less AsyncEnumerable.GroupJoin returning IGrouping.
src/libraries/System.Linq.AsyncEnumerable/src/System/Linq/RightJoin.csImplements tuple-returning AsyncEnumerable.RightJoin overloads (sync+async key selectors).
src/libraries/System.Linq.AsyncEnumerable/src/System/Linq/LeftJoin.csImplements tuple-returning AsyncEnumerable.LeftJoin overloads (sync+async key selectors).
src/libraries/System.Linq.AsyncEnumerable/src/System/Linq/Join.csImplements tuple-returning AsyncEnumerable.Join overloads (sync+async key selectors).
src/libraries/System.Linq.AsyncEnumerable/src/System/Linq/GroupJoin.csImplements selector-less AsyncEnumerable.GroupJoin returning IGrouping + wrapper grouping type.
src/libraries/System.Linq.AsyncEnumerable/ref/System.Linq.AsyncEnumerable.csUpdates System.Linq.AsyncEnumerable reference assembly with new overloads.
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Fix failing AsyncEnumerable tests
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Pull request overview
Copilot reviewed 24 out of 24 changed files in this pull request and generated 7 comments.
Comment threadsrc/libraries/System.Linq/tests/RightJoinTests.cs
Comment threadsrc/libraries/System.Linq/tests/LeftJoinTests.cs
Comment threadsrc/libraries/System.Linq.Queryable/tests/RightJoinTests.cs
Comment threadsrc/libraries/System.Linq.Queryable/tests/RightJoinTests.cs
Comment threadsrc/libraries/System.Linq.Queryable/tests/LeftJoinTests.cs
Comment threadsrc/libraries/System.Linq.Queryable/tests/LeftJoinTests.cs
Comment threadsrc/libraries/System.Linq.AsyncEnumerable/tests/JoinTests.cs
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from rojiApril 9, 2026 16:36
@eiriktsarpalis
Fix swapped tuple field order in JoinTests expected sequence
7cb9b7e
The resultSelector lambda had its parameter names swapped relative to
the actual (outer, inner) positions, producing reversed concatenation
in the expected sequence.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

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LGTM, thanks!
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/ba-g test failures are unrelated.
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