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

Copilot

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)

@jeffhandley

…idation attributes (#132853) Backport of #132764 to `release/11.0`. API proposal: #132605 /cc @jeffhandley @oroztocil ## Customer Impact - [x] Customer reported - [ ] Found internally .NET 11 introduces first-class localization support in `Microsoft.Extensions.Validation`, consumed by Minimal APIs and Blazor. However, DataAnnotations does not expose a shared way for a caller to supply a localized message template while allowing each validation attribute to provide its own placeholder arguments. Without this change, the .NET 11 localization implementation must retain generated per-attribute formatting switches, other hosts cannot reuse the same primitive, and duplicated formatting knowledge can diverge from the real attribute behavior. One existing example is `FileExtensionsAttribute`, where the attribute supplies normalized, dot-prefixed extensions while duplicated upper-layer formatters have supplied the raw property value. The customer scenario has been requested repeatedly: - dotnet/aspnetcore#4848 - dotnet/aspnetcore#12158 - #72469 - dotnet/aspnetcore#66392 This backport adds the API-approved `ValidationAttribute.FormatMessage` primitive and preserves the attribute-specific formatting contract for built-in attributes and Options source-generated replicas. We believe this meets the .NET 11 RC2 bug bar as: - Significant customer feedback on a feature new in the release. - A significantly incomplete message-presentation scenario in DataAnnotations that affects the new .NET 11 validation stack, including localization in MEV, Minimal APIs, and Blazor. ## Regression - [ ] Yes - [x] No This is not a regression from .NET 10. The API and the first-class `Microsoft.Extensions.Validation` localization scenario are new in .NET 11. ## Testing On `main`: - `System.ComponentModel.Annotations` built successfully. - `System.ComponentModel.Annotations.Tests`: 1,008 passed, 0 failed. - `Microsoft.Extensions.Options` built successfully. - `Microsoft.Extensions.Options.Tests`: 177 net11 tests and 158 net481 tests passed. - `Microsoft.Extensions.Options.SourceGeneration.Unit.Tests`: 103 net11 tests and 82 net481 tests passed, with one expected conditional skip. - `Microsoft.Extensions.Options.SourceGeneration.Tests`: 68 net11 tests and 68 net481 tests passed. - Generated replicas were compiled and executed for C# 10 and C# 11. - The .NET Framework generated output remains unchanged. The same component tests and release-branch CI will validate the backport on `release/11.0`. ## Risk Low-to-moderate. The change adds an API-reviewed public virtual method and explicit overrides on the built-in attributes that require additional format arguments. It is additive and removes no existing surface. Existing `FormatErrorMessage` behavior, argument ordering, and `CurrentCulture` formatting remain unchanged. The Options source generator emits matching overrides only when the target compilation exposes the new API, leaving down-level and .NET Framework output unchanged. The main implementation risks are public virtual dispatch and source-generator parity. These are mitigated by: - API approval in #132605. - Technical review and approval on #132764. - Source/ref signature checks. - Direct tests of virtual dispatch and every built-in argument mapping. - Compile-load-invoke tests for generated replicas. - Complete net11 and net481 source-generator test coverage. No package references, dependencies, or package-authoring project settings change. > [!NOTE] > This pull request description was generated with GitHub Copilot. Co-authored-by: Viviana Dueñas <50237907+ViveliDuCh@users.noreply.github.com> Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: 524df8bb-0555-4425-b73f-bc8340d0dfc2

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

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

dotnet-policy-serviceBot assigned ViveliDuCh Aug 25, 2026

Copilotstarted 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

CopilotAI 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 c3ab07bCompare August 25, 2026 21:54

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Comment threadsrc/libraries/Microsoft.Extensions.Options/tests/SourceGeneration.Unit.Tests/Main.cs
Comment threadsrc/libraries/System.ComponentModel.Annotations/ref/System.ComponentModel.Annotations.cs

CopilotAI 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 43ba3c4Compare August 26, 2026 04:51

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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 threadsrc/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
Open

oroztocil approved these changes Aug 26, 2026
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CopilotAI review requested due to automatic review settings August 26, 2026 15:54

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

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

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

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

github-actionsBot mentioned this pull request Aug 27, 2026
[release/11.0] Add message template formatting to DataAnnotations validation attributes #132853
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dotnet-maestroBot mentioned this pull request Aug 28, 2026
[main] Source code updates from dotnet/runtime dotnet/dotnet#8790
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dotnet-milestone-botBot added this to the 12.0-preview1 milestone Aug 28, 2026

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ViveliDuCh commented Aug 25, 2026

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