Consider the impact of C# 11's required properties on model binding / validation

[pranavkm]

Feature: https://github.com/dotnet/csharplang/blob/main/proposals/required-members.md

Using this keyword appears as an attribute in the generated code. We could envision reading it and treated it as the equivalent of BindRequiredAttribute (this property must have a value).

[ghost]

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[ghost]

Thanks for contacting us.

We're moving this issue to the .NET 8 Planning milestone for future evaluation / consideration. We would like to keep this around to collect more feedback, which can help us with prioritizing this work. We will re-evaluate this issue, during our next planning meeting(s).
If we later determine, that the issue has no community involvement, or it's very rare and low-impact issue, we will close it - so that the team can focus on more important and high impact issues.
To learn more about what to expect next and how this issue will be handled you can read more about our triage process here.

[captainsafia]

Another thing to add to the list now that we have support for AsParameters in minimal is to make sure that the required keyword is respected on properties that are passed in with the optionality checks that are provided in the framework.

[captainsafia]

@brunolins16 and I just met to discuss this.

One thing we noted in our investigation is that it is important to have nullability disabled while assessing the impacted of the required property, since our support for inferring requiredness from nullability can mask behaviors.

Some other notes include:

• We need to add a check for RequiredMember in the PropertyAsParameterInfo implementation.
• We discovered a bug in MVC model binding where when nullability is enabled and the validation layer infers that a parameters is required, model binding will still assume it is option. This is unrelated to the required members support but is a bug in our binding logic in general. @brunolins16 will file an issue.
• For FromBody arguments in MVC, model binding will fail appropriately when the user fails to provide a required member because the serializer will fail.
  • Update: we decided that we should have more first class support for RequiredMember in the binder so we're not relying on the behavior of the serializer to respect the property.
• For FromQuery and FromRoute arguments in a model, MVC will not respect the RequriedMember attribute.