ASP.NET Core 10.0: Built-in Validation with IValidatableObject

[jaliyaudagedara]

Is there an existing issue for this?

• I have searched the existing issues

Describe the bug

What's new in ASP.NET Core in .NET 10 in states the following for Validation support in Minimal APIs.

So consider the below sample code.

using System.ComponentModel.DataAnnotations;

WebApplicationBuilder builder = WebApplication.CreateBuilder(args);

builder.Services.AddValidation();

WebApplication app = builder. Build();

app.MapPost("/employees", (Employee employee) =>
{
    return Results.Ok(employee);
});

app.Run();

public class Employee : IValidatableObject
{
    public string Name { get; set; }

    public IEnumerable<ValidationResult> Validate(ValidationContext validationContext)
    {
        if (string.IsNullOrEmpty(Name))
        {
            yield return new ValidationResult("Name cannot be null or empty.", [nameof(Name)]);
        }
    }
}

If I invoke the above endpoint with empty name,

POST {{WebApplication1_HostAddress}}/employees
Content-Type: application/json
{
    "name": ""
}

The validation isn't kicking in as part of model binding.

I can do the validation manually,

app.MapPost("/employees", (Employee employee) =>
{
    var validationResults = new List<ValidationResult>();
    var validationContext = new ValidationContext(employee);

    if (!Validator.TryValidateObject(employee, validationContext, validationResults, validateAllProperties: true))
    {
        return Results.ValidationProblem(validationResults.ToDictionary(
            x => x.MemberNames.FirstOrDefault() ?? "",
            x => new[] { x.ErrorMessage ?? "Invalid value." }));
    }

    return Results.Ok(employee);
});

But then I don't need to register builder.Services.AddValidation().

Expected Behavior

If validation is enabled via builder.Services.AddValidation(), as part of model binding on a type that implements IValidatableObject, validation should kick in automatically.

Steps To Reproduce

Given above

Exceptions (if any)

No response

.NET Version

10.0.100-preview.7.25380.108

Anything else?

No response

[MihuBot]

I'm a bot. Here is a possible related and/or duplicate issue (I may be wrong):

• Update Minimal API validation logic for backwards compatibility #62584

[oroztocil]

@jaliyaudagedara Thank you for reporting the issue.

It seems that when you have a type that is validated only with the IValidatbleObject method (i.e. the type has no property which itself has a validation attribute), then the validation source generator does not create the necessary code for that type. This leads to the validation rule being ignored during run-time. You can check that when you add a property with a validation attribute to the model class the IValidatbleObject validation itself starts to work.

We are going to fix this issue in RC2.

[jaliyaudagedara]

@oroztocil

Thanks for confirming the issue.

Yes, it works as expected with something like below,

public class Employee : IValidatableObject
{
    // Use a System.ComponentModel.DataAnnotation, this triggers the validation for `Name` as well.
    [Range(1, int.MaxValue)]
    public int EmployeeId { get; set; }

    public string Name { get; set; }

    public IEnumerable<ValidationResult> Validate(ValidationContext validationContext)
    {
        if (string.IsNullOrEmpty(Name))
        {
            yield return new ValidationResult("Name cannot be null or empty.", [nameof(Name)]);
        }
    }
}