Add LINQ `FirstOrDefault` support parity across generic NS collections#25509

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copilot/fix-linq-methods-inconsistent-ns-collections

Copilot AI commented May 22, 2026 •

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Understand the issue: NS generic collections (NSSet<T>, NSMutableSet<T>, NSArray<T>, NSMutableArray<T>, NSOrderedSet<T>, NSMutableOrderedSet<T>) inherit from non-generic base classes that implement IEnumerable<NSObject>, causing LINQ type-inference ambiguity
Review existing FirstOrDefault extension overloads in NSCollectionLinqExtensions.cs
Expand NSCollectionLinqExtensions.cs with all common LINQ method overloads for all 6 collection types (First, FirstOrDefault, Last, LastOrDefault, Single, SingleOrDefault, ElementAt, ElementAtOrDefault, Any, All, Count, LongCount, Where, Select, OrderBy, OrderByDescending, Skip, SkipWhile, Take, TakeWhile, Distinct, Reverse, Concat, ToList, ToArray, Aggregate), each with XML docs
Add comprehensive LINQ tests in tests/monotouch-test/Foundation/NSCollectionLinqTest.cs covering all 6 generic NS collections
Validate the build compiles


          Initial plan

080ebc0

Copilot AI assigned Copilot and rolfbjarne

Copilot started work on behalf of rolfbjarne

May 22, 2026 14:54

Copilot AI linked an issue

that may be closed by this pull request

System.Linq methods on NS collections is inconsistent #4597

Open

Copilot AI and others added 2 commits

May 22, 2026 15:07


          Add LINQ FirstOrDefault support wrappers for NS collection generics

64da99f

Agent-Logs-Url: https://github.com/dotnet/macios/sessions/04597ed5-86b1-4feb-b522-8990c6006023

Co-authored-by: rolfbjarne <249268+rolfbjarne@users.noreply.github.com>


          Align generic type naming in NS collection LINQ extensions

c40d839

Agent-Logs-Url: https://github.com/dotnet/macios/sessions/04597ed5-86b1-4feb-b522-8990c6006023

Co-authored-by: rolfbjarne <249268+rolfbjarne@users.noreply.github.com>

Copilot AI changed the title ~~[WIP] Fix inconsistent LINQ methods on NS collections~~ Add LINQ FirstOrDefault support parity across generic NS collections

Copilot finished work on behalf of rolfbjarne

May 22, 2026 15:09

Copilot AI requested a review from rolfbjarne

May 22, 2026 15:09

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Copilot started work on behalf of rolfbjarne

May 25, 2026 07:48

Copilot finished work on behalf of rolfbjarne

May 25, 2026 07:49

Copilot started work on behalf of rolfbjarne

May 25, 2026 10:38

Copilot finished work on behalf of rolfbjarne

May 25, 2026 10:39

Copilot started work on behalf of rolfbjarne

May 25, 2026 10:43

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May 25, 2026 10:44

Copilot started work on behalf of rolfbjarne

May 25, 2026 11:08

Copilot finished work on behalf of rolfbjarne

May 25, 2026 11:10

Copilot started work on behalf of rolfbjarne

May 25, 2026 11:16


          Add all LINQ method overloads with XML docs and tests for all 6 NS ge…

21dd1ba

…neric collections

Agent-Logs-Url: https://github.com/dotnet/macios/sessions/64b2c1cf-9d19-4995-a591-9392aad2cfc5

Co-authored-by: rolfbjarne <249268+rolfbjarne@users.noreply.github.com>

Copilot finished work on behalf of rolfbjarne

May 25, 2026 11:52

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rolfbjarne and others added 2 commits

May 27, 2026 17:30


          Fix build: use ObjCRuntime.INativeObject in LINQ extension constraints

14c2c6d

INativeObject is defined in the ObjCRuntime namespace, not Foundation.
The generic type constraints on all 228 extension methods were referencing
Foundation.INativeObject which doesn't exist, causing CS0234/CS0311 errors.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>


          Auto-format source code

56709b2

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vs-mobiletools-engineering-service2 commented May 27, 2026

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✅ [PR Build #56709b2] Build passed (Detect API changes) ✅

Pipeline on Agent
Hash: 56709b2e806746948448b35df01ab10a3e65d98b [PR build]

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vs-mobiletools-engineering-service2 commented May 27, 2026

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✅ [PR Build #56709b2] Build passed (Build packages) ✅

Pipeline on Agent
Hash: 56709b2e806746948448b35df01ab10a3e65d98b [PR build]

vs-mobiletools-engineering-service2 commented May 27, 2026

Collaborator

✅ API diff for current PR / commit

NET (empty diffs)

iOS: vsdrops gist ( No breaking changes )
tvOS: vsdrops gist ( No breaking changes )
MacCatalyst: vsdrops gist ( No breaking changes )
macOS: vsdrops gist ( No breaking changes )

✅ API diff vs stable

NET (empty diffs)

iOS: vsdrops gist ( No breaking changes )
tvOS: vsdrops gist ( No breaking changes )
MacCatalyst: vsdrops gist ( No breaking changes )
macOS: vsdrops gist ( No breaking changes )

ℹ️ Generator diff

Generator Diff: vsdrops (html) vsdrops (raw diff) gist (raw diff) - Please review changes)

Pipeline on Agent
Hash: 56709b2e806746948448b35df01ab10a3e65d98b [PR build]

vs-mobiletools-engineering-service2 commented May 27, 2026

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🔥 [PR Build #56709b2] Build failed (Build macOS tests) 🔥

Build failed for the job 'Build macOS tests' (with job status 'Failed')

Pipeline on Agent
Hash: 56709b2e806746948448b35df01ab10a3e65d98b [PR build]

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vs-mobiletools-engineering-service2 commented May 27, 2026

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🔥 [CI Build #56709b2] Test results 🔥

Test results

❌ Tests failed on VSTS: test results

5 tests crashed, 87 tests failed, 71 tests passed.

Failures

❌ cecil tests

1 tests failed, 0 tests passed.

Failed tests

Cecil-based tests: Failed (Execution failed with exit code 1)
- Cecil.Tests.Documentation.VerifyEveryVisibleMemberIsDocumented: Found 1 undocumented APIs (not known failures) and 0 APIs that were marked as known failures but are now documented. If this is ...

Html Report (VSDrops) Download

❌ dotnettests tests (iOS)

1 tests failed, 0 tests passed.

Failed tests

DotNet tests: Failed (Execution failed with exit code 1)
- Xamarin.Tests.DotNetProjectTest.BuildFatMonoTouchTest(iOS,"iossi...: 'dotnet build' failed with exit code 1
  Full command: /Users/builder/azdo/_work/1/s/macios/builds/downloads/dotnet-sdk-10.0.301-s...
- Xamarin.Tests.DotNetProjectTest.PublishAotMonoTouchTest_NoIL2009...: 'dotnet build' failed with exit code 1
  Full command: /Users/builder/azdo/_work/1/s/macios/builds/downloads/dotnet-sdk-10.0.301-s...

Html Report (VSDrops) Download

❌ dotnettests tests (MacCatalyst)

1 tests failed, 0 tests passed.

Failed tests

DotNet tests: Failed (Execution failed with exit code 1)
- Xamarin.Tests.DotNetProjectTest.BuildFatMonoTouchTest(MacCatalys...: 'dotnet build' failed with exit code 1
  Full command: /Users/builder/azdo/_work/3/s/macios/builds/downloads/dotnet-sdk-10.0.301-s...
- Xamarin.Tests.DotNetProjectTest.PublishAotMonoTouchTest_NoIL2009...: 'dotnet build' failed with exit code 1
  Full command: /Users/builder/azdo/_work/3/s/macios/builds/downloads/dotnet-sdk-10.0.301-s...

Html Report (VSDrops) Download

❌ dotnettests tests (macOS)

1 tests failed, 0 tests passed.

Failed tests

DotNet tests: Failed (Execution failed with exit code 1)
- Xamarin.Tests.DotNetProjectTest.BuildFatMonoTouchTest(MacOSX,"os...: 'dotnet build' failed with exit code 1
  Full command: /Users/builder/azdo/_work/1/s/macios/builds/downloads/dotnet-sdk-10.0.301-s...
- Xamarin.Tests.DotNetProjectTest.PublishAotMonoTouchTest_NoIL2009...: 'dotnet build' failed with exit code 1
  Full command: /Users/builder/azdo/_work/1/s/macios/builds/downloads/dotnet-sdk-10.0.301-s...

Html Report (VSDrops) Download

❌ dotnettests tests (tvOS)

1 tests failed, 0 tests passed.

Failed tests

DotNet tests: Failed (Execution failed with exit code 1)
- Xamarin.Tests.DotNetProjectTest.PublishAotMonoTouchTest_NoIL2009...: 'dotnet build' failed with exit code 1
  Full command: /Users/builder/azdo/_work/3/s/macios/builds/downloads/dotnet-sdk-10.0.301-s...

Html Report (VSDrops) Download

❌ introspection tests

6 tests failed, 0 tests passed.

Failed tests

introspection/macOS/Debug: Failed (Test run failed.
Tests run: 34 Passed: 31 Inconclusive: 0 Failed: 1 Ignored: 2)
introspection/Mac Catalyst/Debug: Failed (Test run failed.
Tests run: 43 Passed: 38 Inconclusive: 0 Failed: 1 Ignored: 4)
introspection/iOS - simulator/Debug: LaunchTimedOut
introspection/iOS - simulator/Debug (ARM64): LaunchTimedOut
introspection/tvOS - simulator/Debug: LaunchTimedOut
introspection/tvOS - simulator/Debug (ARM64): LaunchTimedOut

Html Report (VSDrops) Download

❌ monotouch tests (iOS)

18 tests failed, 0 tests passed.

Failed tests

monotouch-test/iOS - simulator/Debug: BuildFailure
monotouch-test/iOS - simulator/Release (link sdk): BuildFailure
monotouch-test/iOS - simulator/Release (link all): BuildFailure
monotouch-test/iOS - simulator/Debug (LinkSdk): BuildFailure
monotouch-test/iOS - simulator/Debug (static registrar): BuildFailure
monotouch-test/iOS - simulator/Release (all optimizations): BuildFailure
monotouch-test/iOS - simulator/Debug (ARM64): BuildFailure ( (failed to parse the logs: The Writer is closed or in error state.))
monotouch-test/iOS - simulator/Release (NativeAOT, ARM64): BuildFailure ( (failed to parse the logs: The Writer is closed or in error state.))
monotouch-test/iOS - simulator/Release (trimmable static registrar, NativeAOT, ARM64): BuildFailure ( (failed to parse the logs: The Writer is closed or in error state.))
monotouch-test/iOS - simulator/Debug (managed static registrar): BuildFailure
monotouch-test/iOS - simulator/Release (managed static registrar, all optimizations): BuildFailure
monotouch-test/iOS - simulator/Release (NativeAOT, x64): BuildFailure ( (failed to parse the logs: The Writer is closed or in error state.))
monotouch-test/iOS - simulator/Release (trimmable static registrar, NativeAOT, x64): BuildFailure ( (failed to parse the logs: The Writer is closed or in error state.))
monotouch-test/iOS - simulator/Debug (interpreter): BuildFailure
monotouch-test/iOS - simulator/Release (interpreter): BuildFailure ( (failed to parse the logs: The Writer is closed or in error state.))
monotouch-test/iOS - simulator/Release (compat inline dlfcn): BuildFailure ( (failed to parse the logs: The Writer is closed or in error state.))
monotouch-test/iOS - simulator/Release (strict inline dlfcn, link sdk): BuildFailure
monotouch-test/iOS - simulator/Release (NativeAOT, .NET 11 defaults): BuildFailure

Html Report (VSDrops) Download

❌ monotouch tests (MacCatalyst)

20 tests failed, 0 tests passed.

Failed tests

monotouch-test/Mac Catalyst/Debug: BuildFailure
monotouch-test/Mac Catalyst/Release (link sdk): BuildFailure
monotouch-test/Mac Catalyst/Release (link all): BuildFailure
monotouch-test/Mac Catalyst/Debug (ARM64): BuildFailure
monotouch-test/Mac Catalyst/Debug (managed static registrar): BuildFailure
monotouch-test/Mac Catalyst/Debug (static registrar): BuildFailure ( (failed to parse the logs: The Writer is closed or in error state.))
monotouch-test/Mac Catalyst/Debug (static registrar, ARM64): BuildFailure
monotouch-test/Mac Catalyst/Release (managed static registrar): BuildFailure
monotouch-test/Mac Catalyst/Release (managed static registrar, all optimizations): BuildFailure ( (failed to parse the logs: The Writer is closed or in error state.))
monotouch-test/Mac Catalyst/Release (NativeAOT): BuildFailure
monotouch-test/Mac Catalyst/Release (NativeAOT, ARM64): BuildFailure ( (failed to parse the logs: The Writer is closed or in error state.))
monotouch-test/Mac Catalyst/Release (NativeAOT, x64): BuildFailure ( (failed to parse the logs: The Writer is closed or in error state.))
monotouch-test/Mac Catalyst/Release (trimmable static registrar, NativeAOT): BuildFailure ( (failed to parse the logs: The Writer is closed or in error state.))
monotouch-test/Mac Catalyst/Release (trimmable static registrar, NativeAOT, ARM64): BuildFailure
monotouch-test/Mac Catalyst/Release (trimmable static registrar, NativeAOT, x64): BuildFailure ( (failed to parse the logs: The Writer is closed or in error state.))
monotouch-test/Mac Catalyst/Release (static registrar): BuildFailure
monotouch-test/Mac Catalyst/Release (static registrar, all optimizations): BuildFailure ( (failed to parse the logs: The Writer is closed or in error state.))
monotouch-test/Mac Catalyst/Release (ARM64, LLVM): BuildFailure ( (failed to parse the logs: The Writer is closed or in error state.))
monotouch-test/Mac Catalyst/Debug (interpreter): BuildFailure
monotouch-test/Mac Catalyst/Release (interpreter): BuildFailure

Html Report (VSDrops) Download

❌ monotouch tests (macOS)

20 tests failed, 0 tests passed.

Failed tests

monotouch-test/macOS/Debug: BuildFailure
monotouch-test/macOS/Release (link sdk): BuildFailure ( (failed to parse the logs: The Writer is closed or in error state.))
monotouch-test/macOS/Release (link all): BuildFailure ( (failed to parse the logs: The Writer is closed or in error state.))
monotouch-test/macOS/Debug (ARM64): BuildFailure
monotouch-test/macOS/Debug (managed static registrar): BuildFailure ( (failed to parse the logs: The Writer is closed or in error state.))
monotouch-test/macOS/Debug (trimmable static registrar): BuildFailure ( (failed to parse the logs: The Writer is closed or in error state.))
monotouch-test/macOS/Debug (static registrar): BuildFailure ( (failed to parse the logs: The Writer is closed or in error state.))
monotouch-test/macOS/Debug (static registrar, ARM64): BuildFailure ( (failed to parse the logs: The Writer is closed or in error state.))
monotouch-test/macOS/Release (managed static registrar): BuildFailure
monotouch-test/macOS/Release (trimmable static registrar): BuildFailure ( (failed to parse the logs: The Writer is closed or in error state.))
monotouch-test/macOS/Release (managed static registrar, all optimizations): BuildFailure
monotouch-test/macOS/Release (trimmable static registrar, all optimizations): BuildFailure ( (failed to parse the logs: The Writer is closed or in error state.))
monotouch-test/macOS/Release (NativeAOT): BuildFailure ( (failed to parse the logs: The Writer is closed or in error state.))
monotouch-test/macOS/Release (NativeAOT, ARM64): BuildFailure ( (failed to parse the logs: The Writer is closed or in error state.))
monotouch-test/macOS/Release (NativeAOT, x64): BuildFailure ( (failed to parse the logs: The Writer is closed or in error state.))
monotouch-test/macOS/Release (trimmable static registrar, NativeAOT): BuildFailure ( (failed to parse the logs: The Writer is closed or in error state.))
monotouch-test/macOS/Release (trimmable static registrar, NativeAOT, ARM64): BuildFailure ( (failed to parse the logs: The Writer is closed or in error state.))
monotouch-test/macOS/Release (trimmable static registrar, NativeAOT, x64): BuildFailure ( (failed to parse the logs: The Writer is closed or in error state.))
monotouch-test/macOS/Release (static registrar): BuildFailure ( (failed to parse the logs: The Writer is closed or in error state.))
monotouch-test/macOS/Release (static registrar, all optimizations): BuildFailure ( (failed to parse the logs: The Writer is closed or in error state.))

Html Report (VSDrops) Download

❌ monotouch tests (tvOS)

18 tests failed, 0 tests passed.

Failed tests

monotouch-test/tvOS - simulator/Debug: BuildFailure
monotouch-test/tvOS - simulator/Release (link sdk): BuildFailure
monotouch-test/tvOS - simulator/Release (link all): BuildFailure
monotouch-test/tvOS - simulator/Debug (LinkSdk): BuildFailure
monotouch-test/tvOS - simulator/Debug (static registrar): BuildFailure
monotouch-test/tvOS - simulator/Release (all optimizations): BuildFailure
monotouch-test/tvOS - simulator/Debug (ARM64): BuildFailure
monotouch-test/tvOS - simulator/Release (NativeAOT, ARM64): BuildFailure
monotouch-test/tvOS - simulator/Release (trimmable static registrar, NativeAOT, ARM64): BuildFailure ( (failed to parse the logs: The Writer is closed or in error state.))
monotouch-test/tvOS - simulator/Debug (managed static registrar): BuildFailure
monotouch-test/tvOS - simulator/Release (managed static registrar, all optimizations): BuildFailure ( (failed to parse the logs: The Writer is closed or in error state.))
monotouch-test/tvOS - simulator/Release (NativeAOT, x64): BuildFailure ( (failed to parse the logs: The Writer is closed or in error state.))
monotouch-test/tvOS - simulator/Release (trimmable static registrar, NativeAOT, x64): BuildFailure ( (failed to parse the logs: The Writer is closed or in error state.))
monotouch-test/tvOS - simulator/Debug (interpreter): BuildFailure
monotouch-test/tvOS - simulator/Release (interpreter): BuildFailure
monotouch-test/tvOS - simulator/Release (compat inline dlfcn): BuildFailure
monotouch-test/tvOS - simulator/Release (strict inline dlfcn, link sdk): BuildFailure ( (failed to parse the logs: The Writer is closed or in error state.))
monotouch-test/tvOS - simulator/Release (NativeAOT, .NET 11 defaults): BuildFailure

Html Report (VSDrops) Download

❌ Tests on macOS Monterey (12) tests

🔥 Failed catastrophically on VSTS: test results - mac_monterey (no summary found).

Html Report (VSDrops) Download

❌ Tests on macOS Ventura (13) tests

🔥 Failed catastrophically on VSTS: test results - mac_ventura (no summary found).

Html Report (VSDrops) Download

❌ Tests on macOS Sonoma (14) tests

🔥 Failed catastrophically on VSTS: test results - mac_sonoma (no summary found).

Html Report (VSDrops) Download

❌ Tests on macOS Sequoia (15) tests

🔥 Failed catastrophically on VSTS: test results - mac_sequoia (no summary found).

Html Report (VSDrops) Download

❌ Tests on macOS Tahoe (26) tests

🔥 Failed catastrophically on VSTS: test results - mac_tahoe (no summary found).

Html Report (VSDrops) Download

Successes

✅ dotnettests (Multiple platforms): All 1 tests passed. Html Report (VSDrops) Download
✅ framework: All 2 tests passed. Html Report (VSDrops) Download
✅ fsharp: All 4 tests passed. Html Report (VSDrops) Download
✅ generator: All 5 tests passed. Html Report (VSDrops) Download
✅ interdependent-binding-projects: All 4 tests passed. Html Report (VSDrops) Download
✅ linker (iOS): All 11 tests passed. Html Report (VSDrops) Download
✅ linker (MacCatalyst): All 11 tests passed. Html Report (VSDrops) Download
✅ linker (macOS): All 11 tests passed. Html Report (VSDrops) Download
✅ linker (tvOS): All 11 tests passed. Html Report (VSDrops) Download
✅ msbuild: All 2 tests passed. Html Report (VSDrops) Download
✅ sharpie: All 1 tests passed. Html Report (VSDrops) Download
✅ windows: All 3 tests passed. Html Report (VSDrops) Download
✅ xcframework: All 4 tests passed. Html Report (VSDrops) Download
✅ xtro: All 1 tests passed. Html Report (VSDrops) Download

macOS tests

Linux Build Verification

✅ Linux build succeeded

Pipeline on Agent
Hash: 56709b2e806746948448b35df01ab10a3e65d98b [PR build]

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