ConfigurationManager: preserve descendant-path guard while honoring slash-named entries

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main PR N/A

Description

Configuration collections currently return null for any key containing /, which hides real configuration errors when a slash-containing section/group name is actually declared. This change keeps descendant-path rejection (outer/inner) while allowing exact slash-named keys present in the collection to flow to normal factory resolution and surface cached ConfigurationErrorsException.

• Lookup guard refinement (section groups)

  • ConfigurationSectionGroupCollection.Get(string) now rejects slash paths only when the key is not an exact member of the collection.

• Lookup guard refinement (sections)

  • Applied the same logic in ConfigurationSectionCollection.Get(string) for parity.

• Regression coverage

  • Added tests for:
    • name lookup and index lookup
    • enumeration behavior
    • CopyTo
    • descendant-path rejection preservation

// before: any slash was rejectedif(name.Contains('/'))returnnull;// after: reject only slash paths that are not exact keys in this collectionif(name.Contains('/')&&BaseGet(name)isnull)returnnull;

Customer Impact

Without this fix, malformed slash-named declarations can be silently surfaced as null entries instead of the expected configuration exception, obscuring configuration failures and making diagnosis harder.

Regression

Yes. This addresses incorrect handling where slash-containing declared names were treated the same as descendant-path access.

Testing

Added focused regression tests covering slash-name name/index access, enumeration, CopyTo, and descendant-path rejection behavior.

Risk

Low. Change is narrowly scoped to key filtering in two collection getters and is covered by targeted behavioral tests for both corrected and preserved paths.

Package authoring no longer needed in .NET 9

IMPORTANT: Starting with .NET 9, you no longer need to edit a NuGet package's csproj to enable building and bump the version.
Keep in mind that we still need package authoring in .NET 8 and older versions.

Note

This PR description was generated with AI/Copilot assistance.

• FixesConfigurationManager should reject or handle sectionGroup names containing '/' #125185

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Review details

• Files reviewed: 3/3 changed files
• Comments generated: 0 new
• Review effort level: Lite

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Review details

Suppressed comments (2)

src/libraries/System.Configuration.ConfigurationManager/src/System/Configuration/ConfigurationSectionGroupCollection.cs:93

• The comment above this guard is now misleading: the code no longer rejects all names containing '/', it only rejects slash-containing names that are not exact members of this collection. Updating the comment will help future maintainers understand why BaseGet(name) is part of the check.

 // prevent GetConfig from returning config not in this collection
if (name.Contains('/') && BaseGet(name) is null)
return null;

src/libraries/System.Configuration.ConfigurationManager/src/System/Configuration/ConfigurationSectionCollection.cs:90

• The comment above this guard is now misleading: the code no longer rejects all names containing '/', it only rejects slash-containing names that are not exact members of this collection. Updating the comment will help clarify why BaseGet(name) is used.

 // prevent GetConfig from returning config not in this collection
if (name.Contains('/') && BaseGet(name) is null)
return null;

• Files reviewed: 3/3 changed files
• Comments generated: 0 new
• Review effort level: Lite

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