[release/8.0] Fix nullable annotation for Validator.TryValidateValue and ValidateValue

[github-actions]

Backport of #91286 to release/8.0

/cc @jeffhandley

Customer Impact

System.ComponentModel.DataAnnotations.Validator has methods for validating individual values against a list of validation attributes; they are ValidateValue and TryValidateValue. Those two methods are annotated as not allowing null values to be validated, and the XML doc comments indicate the value cannot be null as well. The annotation and comment were incorrect though, with the XML doc comment likely copied and pasted from the Object validation members long ago.

Customers haven't historically called these methods directly, with it being more of a framework-level concern to orchestrate validation. With the Options Validation source generator introduced in .NET 8 though, we are now generating code into customers' projects that calls these methods directly so that Reflection can be bypassed at runtime. With the incorrect nullable annotation, we have to generate code that includes a ! on the argument value. Taking this fix in .NET 8, the source generator can potentially stop emitting the ! into the generated code when targeting net8+. (That change is being considered but is not included in this PR).

Testing

Compilation and unit tests succeed. A search across other dotnet org repos found no call sites to update.

Risk

Low. Only affects nullable annotation behavior at design-time, and this relaxes an erroneous annotation in a non-breaking way.

[dotnet-issue-labeler]

Note regarding the new-api-needs-documentation label:

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Issue Details

---

Backport of #91286 to release/8.0

/cc @jeffhandley

Customer Impact

System.ComponentModel.DataAnnotations.Validator has methods for validating individual values against a list of validation attributes; they are ValidateValue and TryValidateValue. Those two methods are annotated as not allowing null values to be validated, and the XML doc comments indicate the value cannot be null as well. The annotation and comment were incorrect though, with the XML doc comment likely copied and pasted from the Object validation members long ago.

Customers haven't historically called these methods directly, with it being more of a framework-level concern to orchestrate validation. With the Options Validation source generator introduced in .NET 8 though, we are now generating code into customers' projects that calls these methods directly so that Reflection can be bypassed at runtime. With the incorrect nullable annotation, we have to generate code that includes a ! on the argument value. Taking this fix in .NET 8, we can stop generating the superfluous ! as customers adopt the source generator.

Testing

Pending: #91286 (comment)

Risk

Author:	github-actions[bot]
Assignees:	-
Labels:	area-System.ComponentModel.DataAnnotations, new-api-needs-documentation
Milestone:	-

[jeffhandley]

@carlossanlop This one's ready for release/8.0