Implement LINQ FullJoin operators - #127236

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eiriktsarpalis merged 4 commits into
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eiriktsarpalis:feature/full-join
May 18, 2026
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Implement LINQ FullJoin operators#127236
eiriktsarpalis merged 4 commits into
dotnet:mainfrom
eiriktsarpalis:feature/full-join

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Fixes#124787.

Summary

  • add FullJoin to Enumerable, Queryable, and AsyncEnumerable
  • use the approved API shape with a single optional IEqualityComparer<TKey>? comparer = null parameter
  • include the corresponding ref updates and test coverage

CopilotAI review requested due to automatic review settings April 21, 2026 18:35
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Pull request overview

Adds a new LINQ FullJoin operator across Enumerable, Queryable, and AsyncEnumerable, including reference-assembly updates and new unit tests, to support full outer join semantics in .NET’s LINQ surface area.

Changes:

  • Introduces Enumerable.FullJoin implementation and Queryable.FullJoin expression-tree entry points.
  • Adds AsyncEnumerable.FullJoin (including async key selector variants) plus ref/csproj wiring.
  • Adds new test coverage for System.Linq, System.Linq.Queryable, and System.Linq.AsyncEnumerable.

Reviewed changes

Copilot reviewed 14 out of 14 changed files in this pull request and generated 3 comments.

Show a summary per file
FileDescription
src/libraries/System.Linq/tests/System.Linq.Tests.csprojIncludes new FullJoinTests.cs in System.Linq test project.
src/libraries/System.Linq/tests/FullJoinTests.csAdds unit tests for Enumerable.FullJoin, including tuple overloads.
src/libraries/System.Linq/src/System/Linq/FullJoin.csImplements Enumerable.FullJoin iterator logic and public APIs.
src/libraries/System.Linq/src/System.Linq.csprojAdds System\\Linq\\FullJoin.cs to the build.
src/libraries/System.Linq/ref/System.Linq.csAdds FullJoin APIs to System.Linq reference assembly.
src/libraries/System.Linq.Queryable/tests/System.Linq.Queryable.Tests.csprojIncludes new FullJoinTests.cs in Queryable test project.
src/libraries/System.Linq.Queryable/tests/FullJoinTests.csAdds unit tests for Queryable.FullJoin (including tuple overloads).
src/libraries/System.Linq.Queryable/src/System/Linq/Queryable.csAdds Queryable.FullJoin methods producing MethodCallExpressions.
src/libraries/System.Linq.Queryable/ref/System.Linq.Queryable.csAdds FullJoin APIs to System.Linq.Queryable reference assembly.
src/libraries/System.Linq.AsyncEnumerable/tests/System.Linq.AsyncEnumerable.Tests.csprojIncludes new FullJoinTests.cs in AsyncEnumerable test project.
src/libraries/System.Linq.AsyncEnumerable/tests/FullJoinTests.csAdds tests for async result-selector overloads (validation/cancellation/etc.).
src/libraries/System.Linq.AsyncEnumerable/src/System/Linq/FullJoin.csImplements AsyncEnumerable.FullJoin (sync + async key selector variants) and tuple overloads.
src/libraries/System.Linq.AsyncEnumerable/src/System.Linq.AsyncEnumerable.csprojAdds System\\Linq\\FullJoin.cs to the build.
src/libraries/System.Linq.AsyncEnumerable/ref/System.Linq.AsyncEnumerable.csAdds FullJoin APIs to System.Linq.AsyncEnumerable reference assembly.

Comment threadsrc/libraries/System.Linq.AsyncEnumerable/src/System/Linq/FullJoin.cs Outdated
Comment threadsrc/libraries/System.Linq.AsyncEnumerable/tests/FullJoinTests.cs
Comment threadsrc/libraries/System.Linq/src/System/Linq/FullJoin.cs Outdated
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Thanks @eiriktsarpalis - LGTM, just one possible fast-path optimization that we might consider doing.

Comment threadsrc/libraries/System.Linq/src/System/Linq/FullJoin.cs
CopilotAI review requested due to automatic review settings April 22, 2026 17:25
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Pull request overview

Copilot reviewed 20 out of 20 changed files in this pull request and generated 3 comments.

Comment threadsrc/libraries/System.Linq/src/System/Linq/FullJoin.cs
Comment threadsrc/libraries/System.Linq/src/System/Linq/FullJoin.cs
Comment threadsrc/libraries/System.Linq.AsyncEnumerable/src/System/Linq/FullJoin.cs
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@copilot resolve the merge conflicts in this pull request

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@copilot resolve the merge conflicts in this pull request

eiriktsarpalisand others added 4 commits May 6, 2026 15:23
@eiriktsarpalis
Implement LINQ FullJoin operators
5e98aa4
Add FullJoin for Enumerable, Queryable, and AsyncEnumerable using the approved optional comparer API shape.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@eiriktsarpalis
Address null-key handling in LINQ FullJoin
05ce945
Preserve unmatched null-key rows in FullJoin and add regression coverage across Enumerable, Queryable, and AsyncEnumerable join operators.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@eiriktsarpalis
Add FullJoin empty-inner fast path
908833b
Avoid building the inner lookup and matched-group set when Enumerable.FullJoin is given Array.Empty<T>() for the inner sequence.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@eiriktsarpalis
Optimize FullJoin empty-sequence paths
19173f2
Add the requested empty-side fast paths for Enumerable and AsyncEnumerable FullJoin, plus targeted async regression coverage.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
CopilotAI review requested due to automatic review settings May 6, 2026 12:38
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Pull request overview

Copilot reviewed 20 out of 20 changed files in this pull request and generated 4 comments.

Comment threadsrc/libraries/System.Linq/src/System/Linq/FullJoin.cs
Comment threadsrc/libraries/System.Linq.Queryable/src/System/Linq/Queryable.cs
Comment threadsrc/libraries/System.Linq.AsyncEnumerable/src/System/Linq/FullJoin.cs
Comment threadsrc/libraries/System.Linq.AsyncEnumerable/src/System/Linq/FullJoin.cs
This was referenced May 6, 2026
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/ba-g test failures are unrelated

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eiriktsarpalis merged commit 1d2108d into dotnet:mainMay 18, 2026
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eiriktsarpalis deleted the feature/full-join branch May 18, 2026 16:32
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Introduce FullJoin() LINQ operator

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, 'i'); if (__m === '*' || __re.test(location.href)) { injectUserscript("// Add copy buttons to all 
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}
} catch(__e) { console.warn('[Userscript:Add Copy Buttons to Code Blocks]', __e); }
})();
(function(){
try {
var __m = "github.com";
var __re = new RegExp('^' + "github\\.com" + '

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Implement LINQ FullJoin operators - #127236
Merged
eiriktsarpalis merged 4 commits into
dotnet:mainfrom 
eiriktsarpalis:feature/full-join
May 18, 2026
Merged
Implement LINQ FullJoin operators#127236
eiriktsarpalis merged 4 commits into
dotnet:mainfrom 
eiriktsarpalis:feature/full-join
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Apr 21, 2026

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This PR description was generated with GitHub Copilot.
Fixes#124787.
Summary
  • add FullJoin to Enumerable, Queryable, and AsyncEnumerable
  • use the approved API shape with a single optional IEqualityComparer<TKey>? comparer = null parameter
  • include the corresponding ref updates and test coverage
CopilotAI
review requested due to automatic review settings
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Pull request overview
Adds a new LINQ FullJoin operator across Enumerable, Queryable, and AsyncEnumerable, including reference-assembly updates and new unit tests, to support full outer join semantics in .NET’s LINQ surface area.
Changes:
  • Introduces Enumerable.FullJoin implementation and Queryable.FullJoin expression-tree entry points.
  • Adds AsyncEnumerable.FullJoin (including async key selector variants) plus ref/csproj wiring.
  • Adds new test coverage for System.Linq, System.Linq.Queryable, and System.Linq.AsyncEnumerable.
Reviewed changes
Copilot reviewed 14 out of 14 changed files in this pull request and generated 3 comments.
Show a summary per file
FileDescription
src/libraries/System.Linq/tests/System.Linq.Tests.csprojIncludes new FullJoinTests.cs in System.Linq test project.
src/libraries/System.Linq/tests/FullJoinTests.csAdds unit tests for Enumerable.FullJoin, including tuple overloads.
src/libraries/System.Linq/src/System/Linq/FullJoin.csImplements Enumerable.FullJoin iterator logic and public APIs.
src/libraries/System.Linq/src/System.Linq.csprojAdds System\\Linq\\FullJoin.cs to the build.
src/libraries/System.Linq/ref/System.Linq.csAdds FullJoin APIs to System.Linq reference assembly.
src/libraries/System.Linq.Queryable/tests/System.Linq.Queryable.Tests.csprojIncludes new FullJoinTests.cs in Queryable test project.
src/libraries/System.Linq.Queryable/tests/FullJoinTests.csAdds unit tests for Queryable.FullJoin (including tuple overloads).
src/libraries/System.Linq.Queryable/src/System/Linq/Queryable.csAdds Queryable.FullJoin methods producing MethodCallExpressions.
src/libraries/System.Linq.Queryable/ref/System.Linq.Queryable.csAdds FullJoin APIs to System.Linq.Queryable reference assembly.
src/libraries/System.Linq.AsyncEnumerable/tests/System.Linq.AsyncEnumerable.Tests.csprojIncludes new FullJoinTests.cs in AsyncEnumerable test project.
src/libraries/System.Linq.AsyncEnumerable/tests/FullJoinTests.csAdds tests for async result-selector overloads (validation/cancellation/etc.).
src/libraries/System.Linq.AsyncEnumerable/src/System/Linq/FullJoin.csImplements AsyncEnumerable.FullJoin (sync + async key selector variants) and tuple overloads.
src/libraries/System.Linq.AsyncEnumerable/src/System.Linq.AsyncEnumerable.csprojAdds System\\Linq\\FullJoin.cs to the build.
src/libraries/System.Linq.AsyncEnumerable/ref/System.Linq.AsyncEnumerable.csAdds FullJoin APIs to System.Linq.AsyncEnumerable reference assembly.
Comment threadsrc/libraries/System.Linq.AsyncEnumerable/src/System/Linq/FullJoin.cs
Outdated

Comment threadsrc/libraries/System.Linq.AsyncEnumerable/tests/FullJoinTests.cs
Comment threadsrc/libraries/System.Linq/src/System/Linq/FullJoin.cs
Outdated


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Thanks @eiriktsarpalis - LGTM, just one possible fast-path optimization that we might consider doing.
Comment threadsrc/libraries/System.Linq/src/System/Linq/FullJoin.cs
CopilotAI
review requested due to automatic review settings
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Pull request overview
Copilot reviewed 20 out of 20 changed files in this pull request and generated 3 comments.
Comment threadsrc/libraries/System.Linq/src/System/Linq/FullJoin.cs
Comment threadsrc/libraries/System.Linq/src/System/Linq/FullJoin.cs
Comment threadsrc/libraries/System.Linq.AsyncEnumerable/src/System/Linq/FullJoin.cs
@eiriktsarpalis
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May 5, 2026

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@copilot resolve the merge conflicts in this pull request

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May 6, 2026

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@copilot resolve the merge conflicts in this pull request
eiriktsarpalisand others
added 4 commits
May 6, 2026 15:23
@eiriktsarpalis
Implement LINQ FullJoin operators
5e98aa4
Add FullJoin for Enumerable, Queryable, and AsyncEnumerable using the approved optional comparer API shape.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@eiriktsarpalis
Address null-key handling in LINQ FullJoin
05ce945
Preserve unmatched null-key rows in FullJoin and add regression coverage across Enumerable, Queryable, and AsyncEnumerable join operators.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@eiriktsarpalis
Add FullJoin empty-inner fast path
908833b
Avoid building the inner lookup and matched-group set when Enumerable.FullJoin is given Array.Empty<T>() for the inner sequence.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@eiriktsarpalis
Optimize FullJoin empty-sequence paths
19173f2
Add the requested empty-side fast paths for Enumerable and AsyncEnumerable FullJoin, plus targeted async regression coverage.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
CopilotAI
review requested due to automatic review settings
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Pull request overview
Copilot reviewed 20 out of 20 changed files in this pull request and generated 4 comments.
Comment threadsrc/libraries/System.Linq/src/System/Linq/FullJoin.cs
Comment threadsrc/libraries/System.Linq.Queryable/src/System/Linq/Queryable.cs
Comment threadsrc/libraries/System.Linq.AsyncEnumerable/src/System/Linq/FullJoin.cs
Comment threadsrc/libraries/System.Linq.AsyncEnumerable/src/System/Linq/FullJoin.cs

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/ba-g test failures are unrelated
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Introduce FullJoin() LINQ operator


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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); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

Skip to content
Implement LINQ FullJoin operators - #127236
Merged
eiriktsarpalis merged 4 commits into
dotnet:mainfrom 
eiriktsarpalis:feature/full-join
May 18, 2026
Merged
Implement LINQ FullJoin operators#127236
eiriktsarpalis merged 4 commits into
dotnet:mainfrom 
eiriktsarpalis:feature/full-join
Conversation
@eiriktsarpalis
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Apr 21, 2026

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This PR description was generated with GitHub Copilot.
Fixes#124787.
Summary
  • add FullJoin to Enumerable, Queryable, and AsyncEnumerable
  • use the approved API shape with a single optional IEqualityComparer<TKey>? comparer = null parameter
  • include the corresponding ref updates and test coverage
CopilotAI
review requested due to automatic review settings
April 21, 2026 18:35
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Pull request overview
Adds a new LINQ FullJoin operator across Enumerable, Queryable, and AsyncEnumerable, including reference-assembly updates and new unit tests, to support full outer join semantics in .NET’s LINQ surface area.
Changes:
  • Introduces Enumerable.FullJoin implementation and Queryable.FullJoin expression-tree entry points.
  • Adds AsyncEnumerable.FullJoin (including async key selector variants) plus ref/csproj wiring.
  • Adds new test coverage for System.Linq, System.Linq.Queryable, and System.Linq.AsyncEnumerable.
Reviewed changes
Copilot reviewed 14 out of 14 changed files in this pull request and generated 3 comments.
Show a summary per file
FileDescription
src/libraries/System.Linq/tests/System.Linq.Tests.csprojIncludes new FullJoinTests.cs in System.Linq test project.
src/libraries/System.Linq/tests/FullJoinTests.csAdds unit tests for Enumerable.FullJoin, including tuple overloads.
src/libraries/System.Linq/src/System/Linq/FullJoin.csImplements Enumerable.FullJoin iterator logic and public APIs.
src/libraries/System.Linq/src/System.Linq.csprojAdds System\\Linq\\FullJoin.cs to the build.
src/libraries/System.Linq/ref/System.Linq.csAdds FullJoin APIs to System.Linq reference assembly.
src/libraries/System.Linq.Queryable/tests/System.Linq.Queryable.Tests.csprojIncludes new FullJoinTests.cs in Queryable test project.
src/libraries/System.Linq.Queryable/tests/FullJoinTests.csAdds unit tests for Queryable.FullJoin (including tuple overloads).
src/libraries/System.Linq.Queryable/src/System/Linq/Queryable.csAdds Queryable.FullJoin methods producing MethodCallExpressions.
src/libraries/System.Linq.Queryable/ref/System.Linq.Queryable.csAdds FullJoin APIs to System.Linq.Queryable reference assembly.
src/libraries/System.Linq.AsyncEnumerable/tests/System.Linq.AsyncEnumerable.Tests.csprojIncludes new FullJoinTests.cs in AsyncEnumerable test project.
src/libraries/System.Linq.AsyncEnumerable/tests/FullJoinTests.csAdds tests for async result-selector overloads (validation/cancellation/etc.).
src/libraries/System.Linq.AsyncEnumerable/src/System/Linq/FullJoin.csImplements AsyncEnumerable.FullJoin (sync + async key selector variants) and tuple overloads.
src/libraries/System.Linq.AsyncEnumerable/src/System.Linq.AsyncEnumerable.csprojAdds System\\Linq\\FullJoin.cs to the build.
src/libraries/System.Linq.AsyncEnumerable/ref/System.Linq.AsyncEnumerable.csAdds FullJoin APIs to System.Linq.AsyncEnumerable reference assembly.
Comment threadsrc/libraries/System.Linq.AsyncEnumerable/src/System/Linq/FullJoin.cs
Outdated

Comment threadsrc/libraries/System.Linq.AsyncEnumerable/tests/FullJoinTests.cs
Comment threadsrc/libraries/System.Linq/src/System/Linq/FullJoin.cs
Outdated


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Thanks @eiriktsarpalis - LGTM, just one possible fast-path optimization that we might consider doing.
Comment threadsrc/libraries/System.Linq/src/System/Linq/FullJoin.cs
CopilotAI
review requested due to automatic review settings
April 22, 2026 17:25
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Pull request overview
Copilot reviewed 20 out of 20 changed files in this pull request and generated 3 comments.
Comment threadsrc/libraries/System.Linq/src/System/Linq/FullJoin.cs
Comment threadsrc/libraries/System.Linq/src/System/Linq/FullJoin.cs
Comment threadsrc/libraries/System.Linq.AsyncEnumerable/src/System/Linq/FullJoin.cs
@eiriktsarpalis
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@copilot resolve the merge conflicts in this pull request

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May 6, 2026

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@copilot resolve the merge conflicts in this pull request
eiriktsarpalisand others
added 4 commits
May 6, 2026 15:23
@eiriktsarpalis
Implement LINQ FullJoin operators
5e98aa4
Add FullJoin for Enumerable, Queryable, and AsyncEnumerable using the approved optional comparer API shape.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@eiriktsarpalis
Address null-key handling in LINQ FullJoin
05ce945
Preserve unmatched null-key rows in FullJoin and add regression coverage across Enumerable, Queryable, and AsyncEnumerable join operators.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@eiriktsarpalis
Add FullJoin empty-inner fast path
908833b
Avoid building the inner lookup and matched-group set when Enumerable.FullJoin is given Array.Empty<T>() for the inner sequence.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@eiriktsarpalis
Optimize FullJoin empty-sequence paths
19173f2
Add the requested empty-side fast paths for Enumerable and AsyncEnumerable FullJoin, plus targeted async regression coverage.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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Pull request overview
Copilot reviewed 20 out of 20 changed files in this pull request and generated 4 comments.
Comment threadsrc/libraries/System.Linq/src/System/Linq/FullJoin.cs
Comment threadsrc/libraries/System.Linq.Queryable/src/System/Linq/Queryable.cs
Comment threadsrc/libraries/System.Linq.AsyncEnumerable/src/System/Linq/FullJoin.cs
Comment threadsrc/libraries/System.Linq.AsyncEnumerable/src/System/Linq/FullJoin.cs

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/ba-g test failures are unrelated
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Introduce FullJoin() LINQ operator


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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('^' + ".*" + '

Skip to content
Implement LINQ FullJoin operators - #127236
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eiriktsarpalis:feature/full-join
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Implement LINQ FullJoin operators#127236
eiriktsarpalis merged 4 commits into
dotnet:mainfrom 
eiriktsarpalis:feature/full-join
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Fixes#124787.
Summary
  • add FullJoin to Enumerable, Queryable, and AsyncEnumerable
  • use the approved API shape with a single optional IEqualityComparer<TKey>? comparer = null parameter
  • include the corresponding ref updates and test coverage
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Pull request overview
Adds a new LINQ FullJoin operator across Enumerable, Queryable, and AsyncEnumerable, including reference-assembly updates and new unit tests, to support full outer join semantics in .NET’s LINQ surface area.
Changes:
  • Introduces Enumerable.FullJoin implementation and Queryable.FullJoin expression-tree entry points.
  • Adds AsyncEnumerable.FullJoin (including async key selector variants) plus ref/csproj wiring.
  • Adds new test coverage for System.Linq, System.Linq.Queryable, and System.Linq.AsyncEnumerable.
Reviewed changes
Copilot reviewed 14 out of 14 changed files in this pull request and generated 3 comments.
Show a summary per file
FileDescription
src/libraries/System.Linq/tests/System.Linq.Tests.csprojIncludes new FullJoinTests.cs in System.Linq test project.
src/libraries/System.Linq/tests/FullJoinTests.csAdds unit tests for Enumerable.FullJoin, including tuple overloads.
src/libraries/System.Linq/src/System/Linq/FullJoin.csImplements Enumerable.FullJoin iterator logic and public APIs.
src/libraries/System.Linq/src/System.Linq.csprojAdds System\\Linq\\FullJoin.cs to the build.
src/libraries/System.Linq/ref/System.Linq.csAdds FullJoin APIs to System.Linq reference assembly.
src/libraries/System.Linq.Queryable/tests/System.Linq.Queryable.Tests.csprojIncludes new FullJoinTests.cs in Queryable test project.
src/libraries/System.Linq.Queryable/tests/FullJoinTests.csAdds unit tests for Queryable.FullJoin (including tuple overloads).
src/libraries/System.Linq.Queryable/src/System/Linq/Queryable.csAdds Queryable.FullJoin methods producing MethodCallExpressions.
src/libraries/System.Linq.Queryable/ref/System.Linq.Queryable.csAdds FullJoin APIs to System.Linq.Queryable reference assembly.
src/libraries/System.Linq.AsyncEnumerable/tests/System.Linq.AsyncEnumerable.Tests.csprojIncludes new FullJoinTests.cs in AsyncEnumerable test project.
src/libraries/System.Linq.AsyncEnumerable/tests/FullJoinTests.csAdds tests for async result-selector overloads (validation/cancellation/etc.).
src/libraries/System.Linq.AsyncEnumerable/src/System/Linq/FullJoin.csImplements AsyncEnumerable.FullJoin (sync + async key selector variants) and tuple overloads.
src/libraries/System.Linq.AsyncEnumerable/src/System.Linq.AsyncEnumerable.csprojAdds System\\Linq\\FullJoin.cs to the build.
src/libraries/System.Linq.AsyncEnumerable/ref/System.Linq.AsyncEnumerable.csAdds FullJoin APIs to System.Linq.AsyncEnumerable reference assembly.
Comment threadsrc/libraries/System.Linq.AsyncEnumerable/src/System/Linq/FullJoin.cs
Outdated

Comment threadsrc/libraries/System.Linq.AsyncEnumerable/tests/FullJoinTests.cs
Comment threadsrc/libraries/System.Linq/src/System/Linq/FullJoin.cs
Outdated


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Thanks @eiriktsarpalis - LGTM, just one possible fast-path optimization that we might consider doing.
Comment threadsrc/libraries/System.Linq/src/System/Linq/FullJoin.cs
CopilotAI
review requested due to automatic review settings
April 22, 2026 17:25
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Pull request overview
Copilot reviewed 20 out of 20 changed files in this pull request and generated 3 comments.
Comment threadsrc/libraries/System.Linq/src/System/Linq/FullJoin.cs
Comment threadsrc/libraries/System.Linq/src/System/Linq/FullJoin.cs
Comment threadsrc/libraries/System.Linq.AsyncEnumerable/src/System/Linq/FullJoin.cs
@eiriktsarpalis
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@copilot resolve the merge conflicts in this pull request

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May 6, 2026

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@copilot resolve the merge conflicts in this pull request
eiriktsarpalisand others
added 4 commits
May 6, 2026 15:23
@eiriktsarpalis
Implement LINQ FullJoin operators
5e98aa4
Add FullJoin for Enumerable, Queryable, and AsyncEnumerable using the approved optional comparer API shape.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@eiriktsarpalis
Address null-key handling in LINQ FullJoin
05ce945
Preserve unmatched null-key rows in FullJoin and add regression coverage across Enumerable, Queryable, and AsyncEnumerable join operators.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@eiriktsarpalis
Add FullJoin empty-inner fast path
908833b
Avoid building the inner lookup and matched-group set when Enumerable.FullJoin is given Array.Empty<T>() for the inner sequence.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@eiriktsarpalis
Optimize FullJoin empty-sequence paths
19173f2
Add the requested empty-side fast paths for Enumerable and AsyncEnumerable FullJoin, plus targeted async regression coverage.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
CopilotAI
review requested due to automatic review settings
May 6, 2026 12:38
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Pull request overview
Copilot reviewed 20 out of 20 changed files in this pull request and generated 4 comments.
Comment threadsrc/libraries/System.Linq/src/System/Linq/FullJoin.cs
Comment threadsrc/libraries/System.Linq.Queryable/src/System/Linq/Queryable.cs
Comment threadsrc/libraries/System.Linq.AsyncEnumerable/src/System/Linq/FullJoin.cs
Comment threadsrc/libraries/System.Linq.AsyncEnumerable/src/System/Linq/FullJoin.cs

This was referenced May 6, 2026

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/ba-g test failures are unrelated
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merged commit 1d2108d
into
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85 of 89 checks passed

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deleted the

feature/full-join

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May 18, 2026 16:32
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Introduce FullJoin() LINQ operator


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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" + '

Skip to content
Implement LINQ FullJoin operators - #127236
Merged
eiriktsarpalis merged 4 commits into
dotnet:mainfrom 
eiriktsarpalis:feature/full-join
May 18, 2026
Merged
Implement LINQ FullJoin operators#127236
eiriktsarpalis merged 4 commits into
dotnet:mainfrom 
eiriktsarpalis:feature/full-join
Conversation
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Apr 21, 2026

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This PR description was generated with GitHub Copilot.
Fixes#124787.
Summary
  • add FullJoin to Enumerable, Queryable, and AsyncEnumerable
  • use the approved API shape with a single optional IEqualityComparer<TKey>? comparer = null parameter
  • include the corresponding ref updates and test coverage
CopilotAI
review requested due to automatic review settings
April 21, 2026 18:35
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Pull request overview
Adds a new LINQ FullJoin operator across Enumerable, Queryable, and AsyncEnumerable, including reference-assembly updates and new unit tests, to support full outer join semantics in .NET’s LINQ surface area.
Changes:
  • Introduces Enumerable.FullJoin implementation and Queryable.FullJoin expression-tree entry points.
  • Adds AsyncEnumerable.FullJoin (including async key selector variants) plus ref/csproj wiring.
  • Adds new test coverage for System.Linq, System.Linq.Queryable, and System.Linq.AsyncEnumerable.
Reviewed changes
Copilot reviewed 14 out of 14 changed files in this pull request and generated 3 comments.
Show a summary per file
FileDescription
src/libraries/System.Linq/tests/System.Linq.Tests.csprojIncludes new FullJoinTests.cs in System.Linq test project.
src/libraries/System.Linq/tests/FullJoinTests.csAdds unit tests for Enumerable.FullJoin, including tuple overloads.
src/libraries/System.Linq/src/System/Linq/FullJoin.csImplements Enumerable.FullJoin iterator logic and public APIs.
src/libraries/System.Linq/src/System.Linq.csprojAdds System\\Linq\\FullJoin.cs to the build.
src/libraries/System.Linq/ref/System.Linq.csAdds FullJoin APIs to System.Linq reference assembly.
src/libraries/System.Linq.Queryable/tests/System.Linq.Queryable.Tests.csprojIncludes new FullJoinTests.cs in Queryable test project.
src/libraries/System.Linq.Queryable/tests/FullJoinTests.csAdds unit tests for Queryable.FullJoin (including tuple overloads).
src/libraries/System.Linq.Queryable/src/System/Linq/Queryable.csAdds Queryable.FullJoin methods producing MethodCallExpressions.
src/libraries/System.Linq.Queryable/ref/System.Linq.Queryable.csAdds FullJoin APIs to System.Linq.Queryable reference assembly.
src/libraries/System.Linq.AsyncEnumerable/tests/System.Linq.AsyncEnumerable.Tests.csprojIncludes new FullJoinTests.cs in AsyncEnumerable test project.
src/libraries/System.Linq.AsyncEnumerable/tests/FullJoinTests.csAdds tests for async result-selector overloads (validation/cancellation/etc.).
src/libraries/System.Linq.AsyncEnumerable/src/System/Linq/FullJoin.csImplements AsyncEnumerable.FullJoin (sync + async key selector variants) and tuple overloads.
src/libraries/System.Linq.AsyncEnumerable/src/System.Linq.AsyncEnumerable.csprojAdds System\\Linq\\FullJoin.cs to the build.
src/libraries/System.Linq.AsyncEnumerable/ref/System.Linq.AsyncEnumerable.csAdds FullJoin APIs to System.Linq.AsyncEnumerable reference assembly.
Comment threadsrc/libraries/System.Linq.AsyncEnumerable/src/System/Linq/FullJoin.cs
Outdated

Comment threadsrc/libraries/System.Linq.AsyncEnumerable/tests/FullJoinTests.cs
Comment threadsrc/libraries/System.Linq/src/System/Linq/FullJoin.cs
Outdated


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Thanks @eiriktsarpalis - LGTM, just one possible fast-path optimization that we might consider doing.
Comment threadsrc/libraries/System.Linq/src/System/Linq/FullJoin.cs
CopilotAI
review requested due to automatic review settings
April 22, 2026 17:25
@eiriktsarpalis
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enabled auto-merge (squash)
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Pull request overview
Copilot reviewed 20 out of 20 changed files in this pull request and generated 3 comments.
Comment threadsrc/libraries/System.Linq/src/System/Linq/FullJoin.cs
Comment threadsrc/libraries/System.Linq/src/System/Linq/FullJoin.cs
Comment threadsrc/libraries/System.Linq.AsyncEnumerable/src/System/Linq/FullJoin.cs
@eiriktsarpalis
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@copilot resolve the merge conflicts in this pull request

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May 6, 2026

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@copilot resolve the merge conflicts in this pull request
eiriktsarpalisand others
added 4 commits
May 6, 2026 15:23
@eiriktsarpalis
Implement LINQ FullJoin operators
5e98aa4
Add FullJoin for Enumerable, Queryable, and AsyncEnumerable using the approved optional comparer API shape.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@eiriktsarpalis
Address null-key handling in LINQ FullJoin
05ce945
Preserve unmatched null-key rows in FullJoin and add regression coverage across Enumerable, Queryable, and AsyncEnumerable join operators.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@eiriktsarpalis
Add FullJoin empty-inner fast path
908833b
Avoid building the inner lookup and matched-group set when Enumerable.FullJoin is given Array.Empty<T>() for the inner sequence.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@eiriktsarpalis
Optimize FullJoin empty-sequence paths
19173f2
Add the requested empty-side fast paths for Enumerable and AsyncEnumerable FullJoin, plus targeted async regression coverage.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
CopilotAI
review requested due to automatic review settings
May 6, 2026 12:38
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Pull request overview
Copilot reviewed 20 out of 20 changed files in this pull request and generated 4 comments.
Comment threadsrc/libraries/System.Linq/src/System/Linq/FullJoin.cs
Comment threadsrc/libraries/System.Linq.Queryable/src/System/Linq/Queryable.cs
Comment threadsrc/libraries/System.Linq.AsyncEnumerable/src/System/Linq/FullJoin.cs
Comment threadsrc/libraries/System.Linq.AsyncEnumerable/src/System/Linq/FullJoin.cs

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/ba-g test failures are unrelated
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merged commit 1d2108d
into
dotnet:mainMay 18, 2026

85 of 89 checks passed

@eiriktsarpalis
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deleted the

feature/full-join

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May 18, 2026 16:32
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Successfully merging this pull request may close these issues.

Introduce FullJoin() LINQ operator


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, 'i');
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); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

Skip to content
Implement LINQ FullJoin operators - #127236
Merged
eiriktsarpalis merged 4 commits into
dotnet:mainfrom 
eiriktsarpalis:feature/full-join
May 18, 2026
Merged
Implement LINQ FullJoin operators#127236
eiriktsarpalis merged 4 commits into
dotnet:mainfrom 
eiriktsarpalis:feature/full-join
Conversation
@eiriktsarpalis
@eiriktsarpaliseiriktsarpalis
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Apr 21, 2026

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This PR description was generated with GitHub Copilot.
Fixes#124787.
Summary
  • add FullJoin to Enumerable, Queryable, and AsyncEnumerable
  • use the approved API shape with a single optional IEqualityComparer<TKey>? comparer = null parameter
  • include the corresponding ref updates and test coverage
CopilotAI
review requested due to automatic review settings
April 21, 2026 18:35
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Pull request overview
Adds a new LINQ FullJoin operator across Enumerable, Queryable, and AsyncEnumerable, including reference-assembly updates and new unit tests, to support full outer join semantics in .NET’s LINQ surface area.
Changes:
  • Introduces Enumerable.FullJoin implementation and Queryable.FullJoin expression-tree entry points.
  • Adds AsyncEnumerable.FullJoin (including async key selector variants) plus ref/csproj wiring.
  • Adds new test coverage for System.Linq, System.Linq.Queryable, and System.Linq.AsyncEnumerable.
Reviewed changes
Copilot reviewed 14 out of 14 changed files in this pull request and generated 3 comments.
Show a summary per file
FileDescription
src/libraries/System.Linq/tests/System.Linq.Tests.csprojIncludes new FullJoinTests.cs in System.Linq test project.
src/libraries/System.Linq/tests/FullJoinTests.csAdds unit tests for Enumerable.FullJoin, including tuple overloads.
src/libraries/System.Linq/src/System/Linq/FullJoin.csImplements Enumerable.FullJoin iterator logic and public APIs.
src/libraries/System.Linq/src/System.Linq.csprojAdds System\\Linq\\FullJoin.cs to the build.
src/libraries/System.Linq/ref/System.Linq.csAdds FullJoin APIs to System.Linq reference assembly.
src/libraries/System.Linq.Queryable/tests/System.Linq.Queryable.Tests.csprojIncludes new FullJoinTests.cs in Queryable test project.
src/libraries/System.Linq.Queryable/tests/FullJoinTests.csAdds unit tests for Queryable.FullJoin (including tuple overloads).
src/libraries/System.Linq.Queryable/src/System/Linq/Queryable.csAdds Queryable.FullJoin methods producing MethodCallExpressions.
src/libraries/System.Linq.Queryable/ref/System.Linq.Queryable.csAdds FullJoin APIs to System.Linq.Queryable reference assembly.
src/libraries/System.Linq.AsyncEnumerable/tests/System.Linq.AsyncEnumerable.Tests.csprojIncludes new FullJoinTests.cs in AsyncEnumerable test project.
src/libraries/System.Linq.AsyncEnumerable/tests/FullJoinTests.csAdds tests for async result-selector overloads (validation/cancellation/etc.).
src/libraries/System.Linq.AsyncEnumerable/src/System/Linq/FullJoin.csImplements AsyncEnumerable.FullJoin (sync + async key selector variants) and tuple overloads.
src/libraries/System.Linq.AsyncEnumerable/src/System.Linq.AsyncEnumerable.csprojAdds System\\Linq\\FullJoin.cs to the build.
src/libraries/System.Linq.AsyncEnumerable/ref/System.Linq.AsyncEnumerable.csAdds FullJoin APIs to System.Linq.AsyncEnumerable reference assembly.
Comment threadsrc/libraries/System.Linq.AsyncEnumerable/src/System/Linq/FullJoin.cs
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Comment threadsrc/libraries/System.Linq.AsyncEnumerable/tests/FullJoinTests.cs
Comment threadsrc/libraries/System.Linq/src/System/Linq/FullJoin.cs
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Thanks @eiriktsarpalis - LGTM, just one possible fast-path optimization that we might consider doing.
Comment threadsrc/libraries/System.Linq/src/System/Linq/FullJoin.cs
CopilotAI
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Pull request overview
Copilot reviewed 20 out of 20 changed files in this pull request and generated 3 comments.
Comment threadsrc/libraries/System.Linq/src/System/Linq/FullJoin.cs
Comment threadsrc/libraries/System.Linq/src/System/Linq/FullJoin.cs
Comment threadsrc/libraries/System.Linq.AsyncEnumerable/src/System/Linq/FullJoin.cs
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@copilot resolve the merge conflicts in this pull request

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@copilot resolve the merge conflicts in this pull request
eiriktsarpalisand others
added 4 commits
May 6, 2026 15:23
@eiriktsarpalis
Implement LINQ FullJoin operators
5e98aa4
Add FullJoin for Enumerable, Queryable, and AsyncEnumerable using the approved optional comparer API shape.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@eiriktsarpalis
Address null-key handling in LINQ FullJoin
05ce945
Preserve unmatched null-key rows in FullJoin and add regression coverage across Enumerable, Queryable, and AsyncEnumerable join operators.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@eiriktsarpalis
Add FullJoin empty-inner fast path
908833b
Avoid building the inner lookup and matched-group set when Enumerable.FullJoin is given Array.Empty<T>() for the inner sequence.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@eiriktsarpalis
Optimize FullJoin empty-sequence paths
19173f2
Add the requested empty-side fast paths for Enumerable and AsyncEnumerable FullJoin, plus targeted async regression coverage.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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Pull request overview
Copilot reviewed 20 out of 20 changed files in this pull request and generated 4 comments.
Comment threadsrc/libraries/System.Linq/src/System/Linq/FullJoin.cs
Comment threadsrc/libraries/System.Linq.Queryable/src/System/Linq/Queryable.cs
Comment threadsrc/libraries/System.Linq.AsyncEnumerable/src/System/Linq/FullJoin.cs
Comment threadsrc/libraries/System.Linq.AsyncEnumerable/src/System/Linq/FullJoin.cs

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/ba-g test failures are unrelated
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Introduce FullJoin() LINQ operator


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, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Remove or un-stick sticky/fixed headers that block content\n(function() {\n function unstick() {\n document.querySelectorAll('header, nav, [role=\"banner\"], .header, .navbar, .sticky, .fixed-top, [style*=\"position: fixed\"], [style*=\"position:sticky\"]').forEach(function(el) {\n if (el.style.position === 'fixed' || el.style.position === 'sticky' || \n getComputedStyle(el).position === 'fixed' || getComputedStyle(el).position === 'sticky') {\n el.style.position = 'static';\n el.style.top = 'auto';\n el.style.zIndex = 'auto';\n }\n });\n }\n \n unstick();\n \n var observer = new MutationObserver(unstick);\n observer.observe(document.body, { childList: true, subtree: true, attributes: true, attributeFilter: ['style', 'class'] });\n})();", "Kill Sticky Headers");
}
} catch(__e) { console.warn('[Userscript:Kill Sticky Headers]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

Skip to content
Implement LINQ FullJoin operators - #127236
Merged
eiriktsarpalis merged 4 commits into
dotnet:mainfrom 
eiriktsarpalis:feature/full-join
May 18, 2026
Merged
Implement LINQ FullJoin operators#127236
eiriktsarpalis merged 4 commits into
dotnet:mainfrom 
eiriktsarpalis:feature/full-join
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Fixes#124787.
Summary
  • add FullJoin to Enumerable, Queryable, and AsyncEnumerable
  • use the approved API shape with a single optional IEqualityComparer<TKey>? comparer = null parameter
  • include the corresponding ref updates and test coverage
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review requested due to automatic review settings
April 21, 2026 18:35
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Pull request overview
Adds a new LINQ FullJoin operator across Enumerable, Queryable, and AsyncEnumerable, including reference-assembly updates and new unit tests, to support full outer join semantics in .NET’s LINQ surface area.
Changes:
  • Introduces Enumerable.FullJoin implementation and Queryable.FullJoin expression-tree entry points.
  • Adds AsyncEnumerable.FullJoin (including async key selector variants) plus ref/csproj wiring.
  • Adds new test coverage for System.Linq, System.Linq.Queryable, and System.Linq.AsyncEnumerable.
Reviewed changes
Copilot reviewed 14 out of 14 changed files in this pull request and generated 3 comments.
Show a summary per file
FileDescription
src/libraries/System.Linq/tests/System.Linq.Tests.csprojIncludes new FullJoinTests.cs in System.Linq test project.
src/libraries/System.Linq/tests/FullJoinTests.csAdds unit tests for Enumerable.FullJoin, including tuple overloads.
src/libraries/System.Linq/src/System/Linq/FullJoin.csImplements Enumerable.FullJoin iterator logic and public APIs.
src/libraries/System.Linq/src/System.Linq.csprojAdds System\\Linq\\FullJoin.cs to the build.
src/libraries/System.Linq/ref/System.Linq.csAdds FullJoin APIs to System.Linq reference assembly.
src/libraries/System.Linq.Queryable/tests/System.Linq.Queryable.Tests.csprojIncludes new FullJoinTests.cs in Queryable test project.
src/libraries/System.Linq.Queryable/tests/FullJoinTests.csAdds unit tests for Queryable.FullJoin (including tuple overloads).
src/libraries/System.Linq.Queryable/src/System/Linq/Queryable.csAdds Queryable.FullJoin methods producing MethodCallExpressions.
src/libraries/System.Linq.Queryable/ref/System.Linq.Queryable.csAdds FullJoin APIs to System.Linq.Queryable reference assembly.
src/libraries/System.Linq.AsyncEnumerable/tests/System.Linq.AsyncEnumerable.Tests.csprojIncludes new FullJoinTests.cs in AsyncEnumerable test project.
src/libraries/System.Linq.AsyncEnumerable/tests/FullJoinTests.csAdds tests for async result-selector overloads (validation/cancellation/etc.).
src/libraries/System.Linq.AsyncEnumerable/src/System/Linq/FullJoin.csImplements AsyncEnumerable.FullJoin (sync + async key selector variants) and tuple overloads.
src/libraries/System.Linq.AsyncEnumerable/src/System.Linq.AsyncEnumerable.csprojAdds System\\Linq\\FullJoin.cs to the build.
src/libraries/System.Linq.AsyncEnumerable/ref/System.Linq.AsyncEnumerable.csAdds FullJoin APIs to System.Linq.AsyncEnumerable reference assembly.
Comment threadsrc/libraries/System.Linq.AsyncEnumerable/src/System/Linq/FullJoin.cs
Outdated

Comment threadsrc/libraries/System.Linq.AsyncEnumerable/tests/FullJoinTests.cs
Comment threadsrc/libraries/System.Linq/src/System/Linq/FullJoin.cs
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Thanks @eiriktsarpalis - LGTM, just one possible fast-path optimization that we might consider doing.
Comment threadsrc/libraries/System.Linq/src/System/Linq/FullJoin.cs
CopilotAI
review requested due to automatic review settings
April 22, 2026 17:25
@eiriktsarpalis
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enabled auto-merge (squash)
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Pull request overview
Copilot reviewed 20 out of 20 changed files in this pull request and generated 3 comments.
Comment threadsrc/libraries/System.Linq/src/System/Linq/FullJoin.cs
Comment threadsrc/libraries/System.Linq/src/System/Linq/FullJoin.cs
Comment threadsrc/libraries/System.Linq.AsyncEnumerable/src/System/Linq/FullJoin.cs
@eiriktsarpalis
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May 5, 2026

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@copilot resolve the merge conflicts in this pull request

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May 6, 2026

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@copilot resolve the merge conflicts in this pull request
eiriktsarpalisand others
added 4 commits
May 6, 2026 15:23
@eiriktsarpalis
Implement LINQ FullJoin operators
5e98aa4
Add FullJoin for Enumerable, Queryable, and AsyncEnumerable using the approved optional comparer API shape.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@eiriktsarpalis
Address null-key handling in LINQ FullJoin
05ce945
Preserve unmatched null-key rows in FullJoin and add regression coverage across Enumerable, Queryable, and AsyncEnumerable join operators.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@eiriktsarpalis
Add FullJoin empty-inner fast path
908833b
Avoid building the inner lookup and matched-group set when Enumerable.FullJoin is given Array.Empty<T>() for the inner sequence.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@eiriktsarpalis
Optimize FullJoin empty-sequence paths
19173f2
Add the requested empty-side fast paths for Enumerable and AsyncEnumerable FullJoin, plus targeted async regression coverage.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
CopilotAI
review requested due to automatic review settings
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Pull request overview
Copilot reviewed 20 out of 20 changed files in this pull request and generated 4 comments.
Comment threadsrc/libraries/System.Linq/src/System/Linq/FullJoin.cs
Comment threadsrc/libraries/System.Linq.Queryable/src/System/Linq/Queryable.cs
Comment threadsrc/libraries/System.Linq.AsyncEnumerable/src/System/Linq/FullJoin.cs
Comment threadsrc/libraries/System.Linq.AsyncEnumerable/src/System/Linq/FullJoin.cs

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/ba-g test failures are unrelated
@eiriktsarpalis
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merged commit 1d2108d
into
dotnet:mainMay 18, 2026

85 of 89 checks passed

@eiriktsarpalis
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deleted the

feature/full-join

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May 18, 2026 16:32
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Introduce FullJoin() LINQ operator


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, 'i');
if (__m === '*' || __re.test(location.href)) {
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");
}
} catch(__e) { console.warn('[Userscript:Universal Dark Mode]', __e); }
})();
})();

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Implement LINQ FullJoin operators - #127236
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eiriktsarpalis merged 4 commits into
dotnet:mainfrom 
eiriktsarpalis:feature/full-join
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Merged
Implement LINQ FullJoin operators#127236
eiriktsarpalis merged 4 commits into
dotnet:mainfrom 
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This PR description was generated with GitHub Copilot.
Fixes#124787.
Summary
  • add FullJoin to Enumerable, Queryable, and AsyncEnumerable
  • use the approved API shape with a single optional IEqualityComparer<TKey>? comparer = null parameter
  • include the corresponding ref updates and test coverage
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review requested due to automatic review settings
April 21, 2026 18:35
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Pull request overview
Adds a new LINQ FullJoin operator across Enumerable, Queryable, and AsyncEnumerable, including reference-assembly updates and new unit tests, to support full outer join semantics in .NET’s LINQ surface area.
Changes:
  • Introduces Enumerable.FullJoin implementation and Queryable.FullJoin expression-tree entry points.
  • Adds AsyncEnumerable.FullJoin (including async key selector variants) plus ref/csproj wiring.
  • Adds new test coverage for System.Linq, System.Linq.Queryable, and System.Linq.AsyncEnumerable.
Reviewed changes
Copilot reviewed 14 out of 14 changed files in this pull request and generated 3 comments.
Show a summary per file
FileDescription
src/libraries/System.Linq/tests/System.Linq.Tests.csprojIncludes new FullJoinTests.cs in System.Linq test project.
src/libraries/System.Linq/tests/FullJoinTests.csAdds unit tests for Enumerable.FullJoin, including tuple overloads.
src/libraries/System.Linq/src/System/Linq/FullJoin.csImplements Enumerable.FullJoin iterator logic and public APIs.
src/libraries/System.Linq/src/System.Linq.csprojAdds System\\Linq\\FullJoin.cs to the build.
src/libraries/System.Linq/ref/System.Linq.csAdds FullJoin APIs to System.Linq reference assembly.
src/libraries/System.Linq.Queryable/tests/System.Linq.Queryable.Tests.csprojIncludes new FullJoinTests.cs in Queryable test project.
src/libraries/System.Linq.Queryable/tests/FullJoinTests.csAdds unit tests for Queryable.FullJoin (including tuple overloads).
src/libraries/System.Linq.Queryable/src/System/Linq/Queryable.csAdds Queryable.FullJoin methods producing MethodCallExpressions.
src/libraries/System.Linq.Queryable/ref/System.Linq.Queryable.csAdds FullJoin APIs to System.Linq.Queryable reference assembly.
src/libraries/System.Linq.AsyncEnumerable/tests/System.Linq.AsyncEnumerable.Tests.csprojIncludes new FullJoinTests.cs in AsyncEnumerable test project.
src/libraries/System.Linq.AsyncEnumerable/tests/FullJoinTests.csAdds tests for async result-selector overloads (validation/cancellation/etc.).
src/libraries/System.Linq.AsyncEnumerable/src/System/Linq/FullJoin.csImplements AsyncEnumerable.FullJoin (sync + async key selector variants) and tuple overloads.
src/libraries/System.Linq.AsyncEnumerable/src/System.Linq.AsyncEnumerable.csprojAdds System\\Linq\\FullJoin.cs to the build.
src/libraries/System.Linq.AsyncEnumerable/ref/System.Linq.AsyncEnumerable.csAdds FullJoin APIs to System.Linq.AsyncEnumerable reference assembly.
Comment threadsrc/libraries/System.Linq.AsyncEnumerable/src/System/Linq/FullJoin.cs
Outdated

Comment threadsrc/libraries/System.Linq.AsyncEnumerable/tests/FullJoinTests.cs
Comment threadsrc/libraries/System.Linq/src/System/Linq/FullJoin.cs
Outdated


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Thanks @eiriktsarpalis - LGTM, just one possible fast-path optimization that we might consider doing.
Comment threadsrc/libraries/System.Linq/src/System/Linq/FullJoin.cs
CopilotAI
review requested due to automatic review settings
April 22, 2026 17:25
@eiriktsarpalis
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Pull request overview
Copilot reviewed 20 out of 20 changed files in this pull request and generated 3 comments.
Comment threadsrc/libraries/System.Linq/src/System/Linq/FullJoin.cs
Comment threadsrc/libraries/System.Linq/src/System/Linq/FullJoin.cs
Comment threadsrc/libraries/System.Linq.AsyncEnumerable/src/System/Linq/FullJoin.cs
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@copilot resolve the merge conflicts in this pull request

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May 6, 2026

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@copilot resolve the merge conflicts in this pull request
eiriktsarpalisand others
added 4 commits
May 6, 2026 15:23
@eiriktsarpalis
Implement LINQ FullJoin operators
5e98aa4
Add FullJoin for Enumerable, Queryable, and AsyncEnumerable using the approved optional comparer API shape.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@eiriktsarpalis
Address null-key handling in LINQ FullJoin
05ce945
Preserve unmatched null-key rows in FullJoin and add regression coverage across Enumerable, Queryable, and AsyncEnumerable join operators.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@eiriktsarpalis
Add FullJoin empty-inner fast path
908833b
Avoid building the inner lookup and matched-group set when Enumerable.FullJoin is given Array.Empty<T>() for the inner sequence.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@eiriktsarpalis
Optimize FullJoin empty-sequence paths
19173f2
Add the requested empty-side fast paths for Enumerable and AsyncEnumerable FullJoin, plus targeted async regression coverage.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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review requested due to automatic review settings
May 6, 2026 12:38
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Pull request overview
Copilot reviewed 20 out of 20 changed files in this pull request and generated 4 comments.
Comment threadsrc/libraries/System.Linq/src/System/Linq/FullJoin.cs
Comment threadsrc/libraries/System.Linq.Queryable/src/System/Linq/Queryable.cs
Comment threadsrc/libraries/System.Linq.AsyncEnumerable/src/System/Linq/FullJoin.cs
Comment threadsrc/libraries/System.Linq.AsyncEnumerable/src/System/Linq/FullJoin.cs

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/ba-g test failures are unrelated
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May 18, 2026 16:32
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Introduce FullJoin() LINQ operator


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