Use the method parameter's runtime (instance) type to find the validator instead of its declared type

[icnocop]

Hi.

Thank you for SharpGrip.FluentValidation.AutoValidation.

Given an ASP.NET MVC endpoint like:

// POST api/Animals
public IActionResult Post([FromBody] CreateAnimalRequest request)
{
    if (!this.ModelState.IsValid)
    {
        return this.ValidationProblem(this.ModelState);
    }
}

With types defined:

public class CreateAnimalRequest
{
}

public class CreatePersonRequest : CreateAnimalRequest
{
    public string Name { get; set; }
}

public class CreateAnimalRequestValidator : AbstractValidator<CreateAnimalRequest>
{
}

public class CreatePersonRequestValidator : AbstractValidator<CreatePersonRequest>
{
}

When an HTTP POST request is sent to api/Animals with the body:

{
    "@odata.type": "#Animals.CreatePersonRequest",
    "Name": "John Doe"
}

Then the CreateAnimalRequestValidator is unexpectedly being used for validation.

I expected CreatePersonRequestValidator to be used instead.

During runtime, request has the correct type CreatePersonRequest.

The problem seems to be that FluentValidationAutoValidationActionFilter.cs uses the method parameter's declared type to find the validator, but it should be using the method parameter's runtime (instance) type instead.

https://github.com/SharpGrip/FluentValidation.AutoValidation/blob/master/FluentValidation.AutoValidation.Mvc/src/Filters/FluentValidationAutoValidationActionFilter.cs#L66C58-L66C71

Thank you.

[mvdgun]

Hi @icnocop,

You are welcome!

Could you provide me with a minimal repro/testing repo where I can use the @odata.type field in the request? From what I can see you are using that field to provide the API with the actual runtime type?

[icnocop]

From what I can see you are using that field to provide the API with the actual runtime type?

Correct. I'm using a custom Newtonsoft.Json.JsonConverter for serialization, but there are other ways.

It seems to be out of scope for the underlying issue, so I left it out for brevity.

I created a test in my pull request that reproduces the issue, and also included a fix.

Thank you.