Honor ConfigurationKeyName in constructor binding

[bbartels]

Constructor binding in Microsoft.Extensions.Configuration.Binder validated and read constructor parameters by CLR property/parameter name, so [ConfigurationKeyName] on a corresponding property could still fail for primary constructors and records. This updates the runtime binder to use the matched property's effective configuration key for parameter value lookup without changing constructor/property matching semantics.

• Runtime binder

  • Keep constructor parameter ↔ property matching based on CLR property names.
  • When a parameter matches a property, bind that parameter from the property's effective configuration key (GetPropertyName(property)), not the raw parameter name.

• Validation / error behavior

  • Preserve existing validation behavior for unannotated properties.
  • Preserve mismatch and ignored-property failures based on constructor parameter names rather than attributed configuration keys.

• Source generator scope

  • No source-generator implementation change.
  • The generator already carries a matched property's ConfigurationKeyName into constructor-parameter binding; this PR only closes the reflection-path parity gap.
  • Intentionally does not expand into separate init-only/source-generator feature work.

• Tests

  • Add a constructor-binding success case for a primary-constructor property annotated with ConfigurationKeyNameAttribute.
  • Keep coverage for the existing unannotated constructor-binding path.
  • Add a negative case proving validation is not widened to unrelated properties that only share the configuration key.

public class Options(string secretKey)
{
    [ConfigurationKeyName("example-secret-key")]
    public string SecretKey { get; } = secretKey;
}

With this change, secretKey is populated from example-secret-key during constructor binding, while constructor/property equivalence checks continue to use SecretKey.

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🔵 Needs a closer look

Avoid repeated property scans during constructor binding by reusing a case-insensitive property map.

Pull request overview

Updates reflection-based constructor binding to honor [ConfigurationKeyName] while preserving CLR-name matching and validation behavior.

Changes:

• Binds constructor parameters using matched properties’ effective configuration keys.
• Adds positive and negative primary-constructor tests.
• Keeps source-generator behavior unchanged.

File summaries

File	Summary
src/libraries/Microsoft.Extensions.Configuration.Binder/tests/Common/ConfigurationBinderTests.TestClasses.cs	Adds annotated primary-constructor test models.
src/libraries/Microsoft.Extensions.Configuration.Binder/tests/Common/ConfigurationBinderTests.cs	Adds constructor-binding success and validation tests.
src/libraries/Microsoft.Extensions.Configuration.Binder/src/ConfigurationBinder.cs	Uses effective property configuration keys. Moderate issue: reuse a case-insensitive property map to avoid repeated quadratic scans.

Review details

Suppressed comments (1)

src/libraries/Microsoft.Extensions.Configuration.Binder/src/ConfigurationBinder.cs:603

• This calls FindMatchingProperty once per constructor parameter even though DoAllParametersHaveEquivalentProperties has already scanned the same property list once per parameter. Compared with the previous HashSet lookup, constructor binding is now O(parameters × properties) for every object (and this path runs for each collection element). Build a case-insensitive name-to-property map once and reuse it for validation and binding to avoid the avoidable quadratic regression.

[!NOTE]
This comment was generated by GitHub Copilot.

                    parameterValues[index] = BindParameter(parameters[index], FindMatchingProperty(parameters[index].Name!, properties)!, type, config, options);

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