Merge main into live

.github/workflows/check-for-build-warnings.yml

@@ -16,10 +16,10 @@
       pull-requests: write
     steps:
       - name: Harden Runner
-        uses: step-security/harden-runner@bf7454d06d71f1098171f2acdf0cd4708d7b5920 # v2.20.0
+        uses: step-security/harden-runner@b09bb98e06d4d774595224525879c09bc6e98c40 # v2.20.1
         with:
           egress-policy: audit
 
-      - uses: dotnet/docs-tools/actions/status-checker@455480c2e1c2fa90ecb711963250f000d66d3251 # main
+      - uses: dotnet/docs-tools/actions/status-checker@main
         with:
           repo_token: ${{ secrets.GITHUB_TOKEN }}

.github/workflows/cleanrepo-orphaned-articles.yml

@@ -17,7 +17,7 @@ jobs:
 
     steps:
       - name: Harden Runner
-        uses: step-security/harden-runner@bf7454d06d71f1098171f2acdf0cd4708d7b5920 # v2.20.0
+        uses: step-security/harden-runner@b09bb98e06d4d774595224525879c09bc6e98c40 # v2.20.1
         with:
           egress-policy: audit
 

.github/workflows/cleanrepo-orphaned-images.yml

@@ -17,7 +17,7 @@ jobs:
 
     steps:
       - name: Harden Runner
-        uses: step-security/harden-runner@bf7454d06d71f1098171f2acdf0cd4708d7b5920 # v2.20.0
+        uses: step-security/harden-runner@b09bb98e06d4d774595224525879c09bc6e98c40 # v2.20.1
         with:
           egress-policy: audit
 

.github/workflows/cleanrepo-orphaned-includes.yml

@@ -17,7 +17,7 @@ jobs:
 
     steps:
       - name: Harden Runner
-        uses: step-security/harden-runner@bf7454d06d71f1098171f2acdf0cd4708d7b5920 # v2.20.0
+        uses: step-security/harden-runner@b09bb98e06d4d774595224525879c09bc6e98c40 # v2.20.1
         with:
           egress-policy: audit
 

.github/workflows/cleanrepo-orphaned-snippets.yml

@@ -17,7 +17,7 @@ jobs:
 
     steps:
       - name: Harden Runner
-        uses: step-security/harden-runner@bf7454d06d71f1098171f2acdf0cd4708d7b5920 # v2.20.0
+        uses: step-security/harden-runner@b09bb98e06d4d774595224525879c09bc6e98c40 # v2.20.1
         with:
           egress-policy: audit
 

.github/workflows/cleanrepo-redirect-hops.yml

@@ -17,7 +17,7 @@ jobs:
 
     steps:
       - name: Harden Runner
-        uses: step-security/harden-runner@bf7454d06d71f1098171f2acdf0cd4708d7b5920 # v2.20.0
+        uses: step-security/harden-runner@b09bb98e06d4d774595224525879c09bc6e98c40 # v2.20.1
         with:
           egress-policy: audit
 

.github/workflows/cleanrepo-relative-links.yml

@@ -17,7 +17,7 @@ jobs:
 
     steps:
       - name: Harden Runner
-        uses: step-security/harden-runner@bf7454d06d71f1098171f2acdf0cd4708d7b5920 # v2.20.0
+        uses: step-security/harden-runner@b09bb98e06d4d774595224525879c09bc6e98c40 # v2.20.1
         with:
           egress-policy: audit
 

.github/workflows/cleanrepo-replace-redirects.yml

@@ -17,7 +17,7 @@ jobs:
 
     steps:
       - name: Harden Runner
-        uses: step-security/harden-runner@bf7454d06d71f1098171f2acdf0cd4708d7b5920 # v2.20.0
+        uses: step-security/harden-runner@b09bb98e06d4d774595224525879c09bc6e98c40 # v2.20.1
         with:
           egress-policy: audit
 

.github/workflows/dependabot-bot.yml

@@ -26,7 +26,7 @@ jobs:
     # Checkout the repo into the workspace within the VM
     steps:
       - name: Harden Runner
-        uses: step-security/harden-runner@bf7454d06d71f1098171f2acdf0cd4708d7b5920 # v2.20.0
+        uses: step-security/harden-runner@b09bb98e06d4d774595224525879c09bc6e98c40 # v2.20.1
         with:
           egress-policy: audit
 

.github/workflows/dependency-review.yml

@@ -17,7 +17,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Harden Runner
-        uses: step-security/harden-runner@bf7454d06d71f1098171f2acdf0cd4708d7b5920 # v2.20.0
+        uses: step-security/harden-runner@b09bb98e06d4d774595224525879c09bc6e98c40 # v2.20.1
         with:
           egress-policy: audit
 

.github/workflows/do-not-merge-label-check.yml

@@ -22,7 +22,7 @@ jobs:
         - 'DO NOT MERGE'
     steps:
       - name: Harden Runner
-        uses: step-security/harden-runner@bf7454d06d71f1098171f2acdf0cd4708d7b5920 # v2.20.0
+        uses: step-security/harden-runner@b09bb98e06d4d774595224525879c09bc6e98c40 # v2.20.1
         with:
           egress-policy: audit
 

.github/workflows/docs-verifier.yml

@@ -10,15 +10,15 @@
     runs-on: ubuntu-latest
     steps:
       - name: Harden Runner
-        uses: step-security/harden-runner@bf7454d06d71f1098171f2acdf0cd4708d7b5920 # v2.20.0
+        uses: step-security/harden-runner@b09bb98e06d4d774595224525879c09bc6e98c40 # v2.20.1
         with:
           egress-policy: audit
 
       - name: Checkout the repository
         uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
 
       - name: Validate
-        uses: dotnet/docs-tools/actions/docs-verifier@1397e452fa0b49e9e52bc2443cd9ec6182a05294 # main
+        uses: dotnet/docs-tools/actions/docs-verifier@main
         env:
           GITHUB_PR_NUMBER: ${{ github.event.pull_request.number }}
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}

.github/workflows/generate-preview-links.yml

@@ -16,10 +16,10 @@
       pull-requests: write
     steps:
       - name: Harden Runner
-        uses: step-security/harden-runner@bf7454d06d71f1098171f2acdf0cd4708d7b5920 # v2.20.0
+        uses: step-security/harden-runner@b09bb98e06d4d774595224525879c09bc6e98c40 # v2.20.1
         with:
           egress-policy: audit
 
-      - uses: dotnet/docs-tools/actions/preview-link-generator@455480c2e1c2fa90ecb711963250f000d66d3251 # main
+      - uses: dotnet/docs-tools/actions/preview-link-generator@main
         with:
           repo_token: ${{ secrets.GITHUB_TOKEN }}

.github/workflows/live-protection.yml

@@ -11,7 +11,7 @@ jobs:
 
     steps:
       - name: Harden Runner
-        uses: step-security/harden-runner@bf7454d06d71f1098171f2acdf0cd4708d7b5920 # v2.20.0
+        uses: step-security/harden-runner@b09bb98e06d4d774595224525879c09bc6e98c40 # v2.20.1
         with:
           egress-policy: audit
 

.github/workflows/markdownlint.yml

@@ -22,12 +22,12 @@ jobs:
 
     steps:
       - name: Harden Runner
-        uses: step-security/harden-runner@bf7454d06d71f1098171f2acdf0cd4708d7b5920 # v2.20.0
+        uses: step-security/harden-runner@b09bb98e06d4d774595224525879c09bc6e98c40 # v2.20.1
         with:
           egress-policy: audit
 
       - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
-      - uses: DavidAnson/markdownlint-cli2-action@6bf21b07787794f89a243495939cd651942aeabe # v24.1.0
+      - uses: DavidAnson/markdownlint-cli2-action@21c1be1b93ad9ed58fa840aacc3f279cde2a72ff # v24.2.0
         with:
           config: ".markdownlint-cli2.jsonc"
           globs: "**/*.md"

.github/workflows/quest-bulk.yml

@@ -28,7 +28,7 @@ jobs:
     if: ${{ github.repository_owner == 'dotnet' }}
     steps:
       - name: Harden Runner
-        uses: step-security/harden-runner@bf7454d06d71f1098171f2acdf0cd4708d7b5920 # v2.20.0
+        uses: step-security/harden-runner@b09bb98e06d4d774595224525879c09bc6e98c40 # v2.20.1
         with:
           egress-policy: audit
 

.github/workflows/quest.yml

@@ -29,7 +29,7 @@ jobs:
 
     steps:
       - name: Harden Runner
-        uses: step-security/harden-runner@bf7454d06d71f1098171f2acdf0cd4708d7b5920 # v2.20.0
+        uses: step-security/harden-runner@b09bb98e06d4d774595224525879c09bc6e98c40 # v2.20.1
         with:
           egress-policy: audit
 

.github/workflows/scorecards.yml

@@ -31,7 +31,7 @@ jobs:
 
     steps:
       - name: Harden Runner
-        uses: step-security/harden-runner@bf7454d06d71f1098171f2acdf0cd4708d7b5920 # v2.20.0
+        uses: step-security/harden-runner@b09bb98e06d4d774595224525879c09bc6e98c40 # v2.20.1
         with:
           egress-policy: audit
 
@@ -71,6 +71,6 @@ jobs:
 
       # Upload the results to GitHub's code scanning dashboard.
       - name: "Upload to code-scanning"
-        uses: github/codeql-action/upload-sarif@e4fba868fa4b1b91e1fdab776edc8cfbe6e9fb81 # v3.29.5
+        uses: github/codeql-action/upload-sarif@5595ccaf912efad79be6eef63a5619ff05969be3 # v3.29.5
         with:
           sarif_file: results.sarif

.github/workflows/snippets5000.yml

@@ -31,7 +31,7 @@ jobs:
     steps:
     # Checkout the repository for the PR
     - name: Harden Runner
-      uses: step-security/harden-runner@bf7454d06d71f1098171f2acdf0cd4708d7b5920 # v2.20.0
+      uses: step-security/harden-runner@b09bb98e06d4d774595224525879c09bc6e98c40 # v2.20.1
       with:
         egress-policy: audit
 

.github/workflows/version-sweep.yml

@@ -34,7 +34,7 @@ jobs:
             # Start the .NET version updater action
             # A composite of the .NET Version Sweeper and the .NET Upgrade Assistant
             - name: Harden Runner
-              uses: step-security/harden-runner@bf7454d06d71f1098171f2acdf0cd4708d7b5920 # v2.20.0
+              uses: step-security/harden-runner@b09bb98e06d4d774595224525879c09bc6e98c40 # v2.20.1
               with:
                 egress-policy: audit
 

.openpublishing.publish.config.json

@@ -55,7 +55,7 @@
     {
       "path_to_root": "_csharpstandard",
       "url": "https://github.com/dotnet/csharpstandard",
-      "branch": "v11-alpha",
+      "branch": "alpha-v12",
       "include_in_build": true,
       "branch_mapping": {}
     },

docfx.json

@@ -49,13 +49,9 @@
             },
             {
                 "files": [
-                    "csharp-12.0/*.md",
                     "csharp-13.0/*.md",
                     "csharp-14.0/*.md",
-                    "closed-hierarchies.md",
-                    "collection-expression-arguments.md",
-                    "labeled-break-continue.md",
-                    "unions.md",
+                    "csharp-15.0/*.md",
                     "unsafe-evolution.md"
                 ],
                 "src": "_csharplang/proposals",
@@ -506,11 +502,11 @@
                 "docs/visual-basic/**/**.{md,yml}": "wiwagn"
             },
             "ms.date": {
-                "_csharpstandard/standard/*.md": "09/12/2025",
-                "_csharplang/proposals/csharp-12.0/*.md": "08/15/2023",
+                "_csharpstandard/standard/*.md": "08/12/2026",
                 "_csharplang/proposals/csharp-13.0/*.md": "10/31/2024",
                 "_csharplang/proposals/csharp-14.0/*.md": "08/06/2025",
-                "_csharplang/proposals/*.md": "06/02/2026",
+                "_csharplang/proposals/csharp-15.0/*.md": "08/12/2026",
+                "_csharplang/proposals/*.md": "08/12/2026",
                 "_roslyn/docs/compilers/CSharp/Compiler Breaking Changes - DotNet 7.md": "11/08/2022",
                 "_roslyn/docs/compilers/CSharp/Compiler Breaking Changes - DotNet 8.md": "11/08/2023",
                 "_roslyn/docs/compilers/CSharp/Compiler Breaking Changes - DotNet 9.md": "11/09/2024",
@@ -619,13 +615,6 @@
                 "_csharpstandard/standard/standard-library.md": "Standard library",
                 "_csharpstandard/standard/documentation-comments.md": "Documentation comments",
                 "_csharpstandard/standard/Bibliography.md": "Bibliography",
-                "_csharplang/proposals/csharp-12.0/primary-constructors.md": "Primary constructors",
-                "_csharplang/proposals/csharp-12.0/using-alias-types.md": "Alias any type",
-                "_csharplang/proposals/csharp-12.0/lambda-method-group-defaults.md": "Optional and parameter array parameters for lambdas and method groups",
-                "_csharplang/proposals/csharp-12.0/inline-arrays.md": "Inline arrays, or fixed sized buffers",
-                "_csharplang/proposals/csharp-12.0/collection-expressions.md": "Collection expressions",
-                "_csharplang/proposals/csharp-12.0/experimental-attribute.md": "Experimental attribute",
-                "_csharplang/proposals/csharp-12.0/ref-readonly-parameters.md": "Ref readonly parameters",
                 "_csharplang/proposals/csharp-13.0/collection-expressions-better-conversion.md": "Better conversion from collection expression",
                 "_csharplang/proposals/csharp-13.0/esc-escape-sequence.md": "String/Character escape sequence '\\e'",
                 "_csharplang/proposals/csharp-13.0/lock-object.md": "Obey lock object semantics for lock statements",
@@ -646,10 +635,11 @@
                 "_csharplang/proposals/csharp-14.0/ignored-directives.md": "Ignored preprocessor directives",
                 "_csharplang/proposals/csharp-14.0/extension-operators.md": "Extension operators",
                 "_csharplang/proposals/csharp-14.0/optional-and-named-parameters-in-expression-trees.md": "Optional and named parameters in expression trees",
-                "_csharplang/proposals/collection-expression-arguments.md": "Collection expression arguments",
-                "_csharplang/proposals/unions.md": "Unions",
-                "_csharplang/proposals/closed-hierarchies.md": "Closed hierarchies",
-                "_csharplang/proposals/labeled-break-continue.md": "Labeled break and continue",
+                "_csharplang/proposals/csharp-15.0/collection-expression-arguments.md": "Collection expression arguments",
+                "_csharplang/proposals/csharp-15.0/unions.md": "Unions",
+                "_csharplang/proposals/csharp-15.0/closed-hierarchies.md": "Closed hierarchies",
+                "_csharplang/proposals/csharp-15.0/labeled-break-continue.md": "Labeled break and continue",
+                "_csharplang/proposals/csharp-15.0/extension-indexers.md": "Extension indexers",
                 "_csharplang/proposals/unsafe-evolution.md": "Memory safety",
                 "_roslyn/docs/compilers/CSharp/Compiler Breaking Changes - DotNet 7.md": "C# compiler breaking changes since C# 10",
                 "_roslyn/docs/compilers/CSharp/Compiler Breaking Changes - DotNet 8.md": "C# compiler breaking changes since C# 11",
@@ -705,13 +695,6 @@
                 "_csharpstandard/standard/standard-library.md": "This appendix lists requirements of the specification library. The C# language relies on these types for some of its behavior.",
                 "_csharpstandard/standard/documentation-comments.md": "This appendix describes XML comments that are used to document your program.",
                 "_csharpstandard/standard/Bibliography.md": "This appendix lists external standards referenced in this specification.",
-                "_csharplang/proposals/csharp-12.0/primary-constructors.md": "Primary constructors put the parameters of one constructor in scope for the whole class or struct to be used for initialization or directly as object state. The trade-off is that any other constructors must call through the primary constructor.",
-                "_csharplang/proposals/csharp-12.0/using-alias-types.md": "Using directives can alias any type, not just named types. You can create aliases for tuple types, generics and more.",
-                "_csharplang/proposals/csharp-12.0/lambda-method-group-defaults.md": "Optional and parameter array parameters for lambdas and method groups",
-                "_csharplang/proposals/csharp-12.0/inline-arrays.md": "Inline arrays provide a general-purpose and safe mechanism for declaring inline arrays within C# classes, structs, and interfaces.",
-                "_csharplang/proposals/csharp-12.0/collection-expressions.md": "Collection expressions provide a concise syntax to initialize collections by defining elements or embedded collections as the source of the new collection's elements.",
-                "_csharplang/proposals/csharp-12.0/experimental-attribute.md": "Use the ExperimentalAttribute attribute to indicate APIs that aren't stable.",
-                "_csharplang/proposals/csharp-12.0/ref-readonly-parameters.md": "Ref readonly parameters enforce that arguments are passed by references, where `in` parameters allow the compiler some flexibiility.",
                 "_csharplang/proposals/csharp-13.0/collection-expressions-better-conversion.md": "Conversions from collection expressions match the element type before matching the collection type.",
                 "_csharplang/proposals/csharp-13.0/esc-escape-sequence.md" : "The sequence '\\e' is now interpreted as the 'ESC' character, character point '0x1b'",
                 "_csharplang/proposals/csharp-13.0/lock-object.md": "Special-case how `System.Threading.Lock` interacts with the `lock` keyword by calling its `EnterScope` method. Add static analysis warnings to prevent accidental misuse of the type where possible.",
@@ -732,10 +715,11 @@
                 "_csharplang/proposals/csharp-14.0/ignored-directives.md": "This proposal allows a source file to include ignored directives. In most cases, ignored directives are used for file-based apps, for example `#!`",
                 "_csharplang/proposals/csharp-14.0/extension-operators.md": "This proposal extends the proposal for extensions to include *extension operators*, where an operator can be an extension member.",
                 "_csharplang/proposals/csharp-14.0/optional-and-named-parameters-in-expression-trees.md": "This proposal allows an expression tree to include named and optional parameters. This enables expression trees to be more flexible in how they are constructed.",
-                "_csharplang/proposals/collection-expression-arguments.md": "This proposal introduces collection expression arguments.",
-                "_csharplang/proposals/unions.md": "This proposal describes union types and union declarations. Unions allow expressing values from a closed set of types with exhaustive pattern matching.",
-                "_csharplang/proposals/closed-hierarchies.md": "This proposal describes closed class hierarchies. A closed class restricts derivation to its declaring assembly, enabling exhaustive `switch` expressions over its direct descendants.",
-                "_csharplang/proposals/labeled-break-continue.md": "This proposal allows `break` and `continue` statements to optionally target an enclosing labeled loop or `switch` statement, enabling cleaner control flow in nested constructs without `goto`.",
+                "_csharplang/proposals/csharp-15.0/collection-expression-arguments.md": "This proposal introduces collection expression arguments.",
+                "_csharplang/proposals/csharp-15.0/unions.md": "This proposal describes union types and union declarations. Unions allow expressing values from a closed set of types with exhaustive pattern matching.",
+                "_csharplang/proposals/csharp-15.0/closed-hierarchies.md": "This proposal describes closed class hierarchies. A closed class restricts derivation to its declaring assembly, enabling exhaustive `switch` expressions over its direct descendants.",
+                "_csharplang/proposals/csharp-15.0/labeled-break-continue.md": "This proposal allows `break` and `continue` statements to optionally target an enclosing labeled loop or `switch` statement, enabling cleaner control flow in nested constructs without `goto`.",
+                "_csharplang/proposals/csharp-15.0/extension-indexers.md": "This proposal extends the proposal for extensions to include *extension indexers*, where an operator can be an extension member.",
                 "_csharplang/proposals/unsafe-evolution.md": "This proposal describes the evolution of memory safety in C#. It ties the `unsafe` context to operations that access unmanaged memory, rather than to the existence of pointer types.",
                 "_roslyn/docs/compilers/CSharp/Compiler Breaking Changes - DotNet 7.md": "Learn about any breaking changes since the initial release of C# 10 and included in C# 11",
                 "_roslyn/docs/compilers/CSharp/Compiler Breaking Changes - DotNet 8.md": "Learn about any breaking changes since the initial release of C# 11 and included in C# 12",
@@ -760,9 +744,9 @@
             "titleSuffix": {
                 "docs/**/*.{md,yml}": ".NET",
                 "_csharpstandard/standard/*.md": "C# language specification",
-                "_csharplang/proposals/csharp-12.0/*.md": "C# feature specifications",
                 "_csharplang/proposals/csharp-13.0/*.md": "C# feature specifications",
                 "_csharplang/proposals/csharp-14.0/*.md": "C# feature specifications",
+                "_csharplang/proposals/csharp-15.0/*.md": "C# feature specifications",
                 "_csharplang/proposals/*.md": "C# feature specifications (preview)",
                 "docs/framework/**/*.{md,yml}": ".NET Framework",
                 "docs/framework/data/adonet/**/*.{md,yml}": "ADO.NET",