Add message template formatting to DataAnnotations validation attributes by ViveliDuCh · Pull Request #132764 · dotnet/runtime

ViveliDuCh · 2026-08-25T21:28:51Z

Summary

Adds the approved ValidationAttribute.FormatMessage API so callers can supply externally localized composite-format strings while each validation attribute remains responsible for providing its placeholder arguments.

Changes

Add ValidationAttribute.FormatMessage([StringSyntax("CompositeFormat")] string format, string name).
Route the base FormatErrorMessage implementation through the new method.
Add overrides for CompareAttribute, FileExtensionsAttribute, LengthAttribute, MaxLengthAttribute, MinLengthAttribute, RangeAttribute, RegularExpressionAttribute, and StringLengthAttribute.
Preserve existing placeholder ordering and CurrentCulture formatting.
Add coverage for supplied formats, virtual dispatch, culture-sensitive formatting, invalid formats, and null arguments.

Existing FormatErrorMessage behavior remains unchanged.

Testing

dotnet build — succeeded with 0 warnings and 0 errors.
dotnet build /t:test .\tests\System.ComponentModel.Annotations.Tests.csproj — 1,008 passed, 0 failed, 0 skipped.

Fixes #132605

Note

This pull request description was generated with GitHub Copilot.

azure-pipelines · 2026-08-25T21:29:35Z

Azure Pipelines: Successfully started running 3 pipeline(s). 13 pipeline(s) were filtered out due to trigger conditions. There may be pipelines that require an authorized user to comment /azp run to run.

dotnet-policy-service · 2026-08-25T21:31:32Z

Tagging subscribers to this area: @dotnet/area-system-componentmodel-dataannotations
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Copilot

Pull request overview

Adds a new public formatting primitive to DataAnnotations validation attributes so callers can supply an external composite-format template while each attribute remains responsible for projecting its own placeholder arguments.

Changes:

Add ValidationAttribute.FormatMessage([StringSyntax("CompositeFormat")] string format, string name) and route the base FormatErrorMessage implementation through it.
Override FormatMessage in built-in attributes that require additional placeholders (e.g., {1}, {2}), preserving existing argument ordering and CurrentCulture formatting behavior.
Add/extend tests to cover supplied formats, virtual dispatch, culture-sensitive formatting, and invalid/null formats.

Reviewed changes

Copilot reviewed 19 out of 19 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
src/libraries/System.ComponentModel.Annotations/src/System/ComponentModel/DataAnnotations/ValidationAttribute.cs	Introduces `FormatMessage` and updates base `FormatErrorMessage` to delegate through it.
src/libraries/System.ComponentModel.Annotations/src/System/ComponentModel/DataAnnotations/CompareAttribute.cs	Overrides `FormatMessage` to supply the other-property display name argument.
src/libraries/System.ComponentModel.Annotations/src/System/ComponentModel/DataAnnotations/FileExtensionsAttribute.cs	Overrides `FormatMessage` to supply normalized/dot-prefixed extensions.
src/libraries/System.ComponentModel.Annotations/src/System/ComponentModel/DataAnnotations/LengthAttribute.cs	Overrides `FormatMessage` to supply min/max length placeholders.
src/libraries/System.ComponentModel.Annotations/src/System/ComponentModel/DataAnnotations/MaxLengthAttribute.cs	Overrides `FormatMessage` to supply the max length placeholder.
src/libraries/System.ComponentModel.Annotations/src/System/ComponentModel/DataAnnotations/MinLengthAttribute.cs	Overrides `FormatMessage` to supply the min length placeholder.
src/libraries/System.ComponentModel.Annotations/src/System/ComponentModel/DataAnnotations/RangeAttribute.cs	Overrides `FormatMessage` to supply converted min/max placeholders.
src/libraries/System.ComponentModel.Annotations/src/System/ComponentModel/DataAnnotations/RegularExpressionAttribute.cs	Overrides `FormatMessage` to supply the regex pattern placeholder.
src/libraries/System.ComponentModel.Annotations/src/System/ComponentModel/DataAnnotations/StringLengthAttribute.cs	Overrides `FormatMessage` to supply maximum/minimum length placeholders and keeps default-template selection in `FormatErrorMessage`.
src/libraries/System.ComponentModel.Annotations/ref/System.ComponentModel.Annotations.cs	Updates public surface area (ref) to include the new virtual and related overrides.
src/libraries/System.ComponentModel.Annotations/tests/System/ComponentModel/DataAnnotations/ValidationAttributeTests.cs	Adds base-level tests for `FormatMessage`, null/invalid format behavior, and `FormatErrorMessage` virtual dispatch.
src/libraries/System.ComponentModel.Annotations/tests/System/ComponentModel/DataAnnotations/CompareAttributeTests.cs	Adds coverage for `CompareAttribute.FormatMessage` argument projection and display-name behavior.
src/libraries/System.ComponentModel.Annotations/tests/System/ComponentModel/DataAnnotations/FileExtensionsAttributeTests.cs	Adds coverage for `FileExtensionsAttribute.FormatMessage` using normalized extensions.
src/libraries/System.ComponentModel.Annotations/tests/System/ComponentModel/DataAnnotations/LengthAttributeTests.cs	Adds coverage for `LengthAttribute.FormatMessage` placeholder projection.
src/libraries/System.ComponentModel.Annotations/tests/System/ComponentModel/DataAnnotations/MaxLengthAttributeTests.cs	Adds coverage for `MaxLengthAttribute.FormatMessage` placeholder projection.
src/libraries/System.ComponentModel.Annotations/tests/System/ComponentModel/DataAnnotations/MinLengthAttributeTests.cs	Adds coverage for `MinLengthAttribute.FormatMessage` placeholder projection.
src/libraries/System.ComponentModel.Annotations/tests/System/ComponentModel/DataAnnotations/RangeAttributeTests.cs	Adds coverage for `RangeAttribute.FormatMessage` conversion and culture-sensitive formatting.
src/libraries/System.ComponentModel.Annotations/tests/System/ComponentModel/DataAnnotations/RegularExpressionAttributeTests.cs	Adds coverage for `RegularExpressionAttribute.FormatMessage` supplying the pattern.
src/libraries/System.ComponentModel.Annotations/tests/System/ComponentModel/DataAnnotations/StringLengthAttributeTests.cs	Adds coverage for `StringLengthAttribute.FormatMessage` placeholder projection and `FormatErrorMessage` behavior.

Add the approved ValidationAttribute.FormatMessage API for caller-supplied composite formats and project built-in attribute arguments through overrides. Cover culture, virtual dispatch, error paths, and source/ref naming consistency. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: 524df8bb-0555-4425-b73f-bc8340d0dfc2

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Pull request overview

Copilot reviewed 19 out of 19 changed files in this pull request and generated no new comments.

tarekgh · 2026-08-25T22:22:41Z

Should we also update the validation attribute replicas emitted by Microsoft.Extensions.Options/gen/Emitter.cs: CompareAttribute, LengthAttribute, MaxLengthAttribute, MinLengthAttribute, and RangeAttribute? They currently inherit the base FormatMessage, which supplies only {0}. When the target exposes the new API, these replicas should conditionally override FormatMessage with the same [StringSyntax(CompositeFormat)] annotation and attribute-specific arguments. Otherwise, they do not preserve the new built-in attribute contract.

Copilot

Pull request overview

Copilot reviewed 30 out of 30 changed files in this pull request and generated 2 comments.

- Detect FormatMessage support from target compilation symbols - Preserve attribute-specific arguments in generated replicas - Share Range initialization between validation and formatting - Add deterministic baselines and runtime regression coverage Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: 524df8bb-0555-4425-b73f-bc8340d0dfc2

Copilot

Pull request overview

Copilot reviewed 30 out of 30 changed files in this pull request and generated 2 comments.

oroztocil

Looks good.

I don't have a strong opinion about the added argument null checks. They are redundant, but also mean the exception is thrown at the level of the public contract. Considering the existing FormatErrorMessage did not have them, I would probably remove them from FormatMessage too.

Rely on string.Format to validate null format strings, use a valid RangeAttribute in null-format coverage, and update generated baselines. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: 524df8bb-0555-4425-b73f-bc8340d0dfc2

Copilot

Pull request overview

Copilot reviewed 30 out of 30 changed files in this pull request and generated no new comments.

tarekgh

LGTM, Thanks!

ViveliDuCh · 2026-08-27T19:28:54Z

/ba-g Remaining unclassified failures are the CompositeMLDsaCngTests Windows failures tracked by known issue #132830, unrelated to this PR.

ViveliDuCh · 2026-08-27T20:04:55Z

/backport to release/11.0

github-actions · 2026-08-27T20:05:03Z

Started backporting to release/11.0 (link to workflow run)

Copilot AI lite review requested due to automatic review settings August 25, 2026 21:28

github-actions Bot added the area-System.ComponentModel.DataAnnotations label Aug 25, 2026

dotnet-policy-service Bot assigned ViveliDuCh Aug 25, 2026

Copilot started reviewing on behalf of ViveliDuCh August 25, 2026 21:29 View session

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Comment thread ...ystem.ComponentModel.Annotations/src/System/ComponentModel/DataAnnotations/RangeAttribute.cs

ViveliDuCh requested review from jeffhandley and oroztocil August 25, 2026 21:41

Copilot AI review requested due to automatic review settings August 25, 2026 21:54

ViveliDuCh force-pushed the api-proposal/dataannotations-format-message branch from db016ee to c3ab07b Compare August 25, 2026 21:54

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Copilot AI review requested due to automatic review settings August 26, 2026 02:07

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Comment thread src/libraries/Microsoft.Extensions.Options/tests/SourceGeneration.Unit.Tests/Main.cs

Comment thread src/libraries/System.ComponentModel.Annotations/ref/System.ComponentModel.Annotations.cs

Copilot AI review requested due to automatic review settings August 26, 2026 04:51

ViveliDuCh force-pushed the api-proposal/dataannotations-format-message branch from 6ec2050 to 43ba3c4 Compare August 26, 2026 04:51

Copilot started reviewing on behalf of ViveliDuCh August 26, 2026 04:51 View session

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Comment thread ...entModel.Annotations/src/System/ComponentModel/DataAnnotations/RegularExpressionAttribute.cs

Comment thread ...omponentModel.Annotations/src/System/ComponentModel/DataAnnotations/StringLengthAttribute.cs

drieseng reviewed Aug 26, 2026

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Comment thread ...omponentModel.Annotations/src/System/ComponentModel/DataAnnotations/StringLengthAttribute.cs Outdated

Comment thread src/libraries/Microsoft.Extensions.Options/gen/Emitter.cs Outdated

This was referenced Aug 26, 2026

Assertion failure in ConnectAsync_WithBuffer_Succeeds on Android/MacCatalyst/tvOS (Mono/CoreCLR/NativeAOT) #125825

Open

Test failure: System.Net.Sockets.Tests.SocketAsyncEventArgsTest.Connect_Parallel_Fails - Completed did not get called in time #132059

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oroztocil approved these changes Aug 26, 2026

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Copilot AI review requested due to automatic review settings August 26, 2026 15:54

Copilot started reviewing on behalf of ViveliDuCh August 26, 2026 15:55 View session

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tarekgh approved these changes Aug 26, 2026

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ViveliDuCh enabled auto-merge (squash) August 26, 2026 17:14

This was referenced Aug 27, 2026

TcpReceiveSendGetsCanceledByDispose timed out #131990

Open

CompositeMLDsaCngTests failing on Windows #132830

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[Test Failure] System.Net.Quic.Tests.MsQuicTests.Client_CertificateWithEphemeralKey_Throws #132831

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ViveliDuCh disabled auto-merge August 27, 2026 19:29

ViveliDuCh merged commit c365a0b into main Aug 27, 2026
78 of 80 checks passed

ViveliDuCh deleted the api-proposal/dataannotations-format-message branch August 27, 2026 19:30

github-actions Bot mentioned this pull request Aug 27, 2026

[release/11.0] Add message template formatting to DataAnnotations validation attributes #132853

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dotnet-maestro Bot mentioned this pull request Aug 28, 2026

[main] Source code updates from dotnet/runtime dotnet/dotnet#8790

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dotnet-milestone-bot Bot added this to the 12.0-preview1 milestone Aug 28, 2026

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ViveliDuCh commented Aug 25, 2026

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