DataAnnotation ignored on Record for validation

[spaasis]

Is there an existing issue for this?

• I have searched the existing issues

Describe the bug

Hi,

I just noticed that validation ignores data annotations on fully defined records but work on classes.

Expected Behavior

DataAnnotations for properties, such as MaxLength, work the same for classes and fully defined records.

Steps To Reproduce

record:

public record Person {
    public Person( string firstName,  string lastName) { //...}

    [MaxLength(50)]
    public string FirstName { get; init; }

    [MaxLength(50)]
    public string LastName { get; init; }
}

api-method:

    [HttpPost]
    public async Task<ActionResult> Post([FromBody] Person input) {
        if (ModelState.IsValid) {
            return Ok();
        }
        return BadRequest(ModelState);
    }

When Person is record and you post a LastName with more than 50 characters, the ModelState is valid.
If Person is changed to a class (without any other changes), the validation error is detected.

Exceptions (if any)

No response

.NET Version

6

Anything else?

No response

[pranavkm]

Are you specifically using a primary constructor (e.g. public record Person(string FirstName, string LastName)? MVC expects these validation attributes to be declared on the constructor parameter: https://docs.microsoft.com/en-us/aspnet/core/mvc/models/model-binding?view=aspnetcore-6.0#constructor-binding-and-record-types

[spaasis]

Hi,
public record Person([property:MaxLength(50)] string FirstName,[property:MaxLength(50)] string LastName); is ignored
public record Person([MaxLength(50)] string FirstName,[MaxLength(50)] string LastName); works
public record Person([param: MaxLength(50)] string FirstName, [param: MaxLength(50)] string LastName); works

So yeah, it seems that when the attribute targets the parameter rather than property it's included.

This makes some things harder (like checking if a record property has a specific parameter) but I'll see if I can work around that. Thanks for pointing me to the right direction