Validation - Analyzer diagnostics for loop iterators captured in closures

Scenario: dotnet/aspnetcore #68490

Manual: dotnet/aspnetcore #68479

Build tested

.NET SDK 11.0.100-preview.7.26381.103

The scenario requires .NET 11 Preview 7 or later.

Sample application

BlazorLoopClosureDemo/ and BlazorLoopClosureDemo.Client/ contain a Blazor Web App using Interactive Server rendering for the validation pages.

Start at /samples/bl0014 to access the complete sample set.

Expected BL0014 warnings

Page	Route	Purpose
@onclick lambda	/samples/bl0014/flagged-onclick	Captures the for iterator in a click handler
Lambda with event args	/samples/bl0014/flagged-args	Captures the iterator alongside event arguments
@bind indexer	/samples/bl0014/flagged-bind	Uses the iterator as a two-way binding index
Child EventCallback	/samples/bl0014/flagged-eventcallback	Captures the iterator in a child callback
Child content	/samples/bl0014/flagged-childcontent	Renders the iterator inside ChildContent

Expected no BL0014 warning

Page	Route	Purpose
Copied local	/samples/bl0014/safe-copied-local	Copies the iterator before capturing it
foreach over a list	/samples/bl0014/safe-foreach	Uses a foreach iteration variable
foreach over Enumerable.Range	/samples/bl0014/safe-range	Uses a range iteration variable
Iterator outside a closure	/samples/bl0014/safe-loop-body-only	Reads the iterator only in the loop body

How to run

From the repository root:

dotnet run --project BlazorLoopClosureDemo/BlazorLoopClosureDemo.csproj

Open the HTTPS URL printed in the console, then navigate to /samples/bl0014.

How to verify the build diagnostic

dotnet clean BlazorLoopClosureDemo.sln -nologo -v:minimal
dotnet build BlazorLoopClosureDemo.sln -t:Rebuild -nologo -v:minimal

Expected result: the five flagged pages produce BL0014 warnings naming the captured iterator. The copied-local, foreach, Enumerable.Range, and loop-body-only pages produce no BL0014 warning.

Configuration tested

• Blazor Web App - Interactive Server
• Visual Studio 2022 and command-line builds
• Published Release output (dotnet publish -c Release)

The diagnostic is produced at compile time and does not vary by render mode.

Evidence

• Screenshots: Evidence/screenshots/
• Interaction recording: Evidence/video/
• Test report: test-report/test-report-68490.md