Difference between ValidationProblem method in Results and TypedResults classes

[McMlok]

Hello,

I want to know why methods ValidationProblem produces different output when they are called on Results or TypedResults class.

Results.ValidationProblem(errorMessages) produces {Microsoft.AspNetCore.Http.HttpResults.ProblemHttpResult} with {Microsoft.AspNetCore.Http.HttpValidationProblemDetails} in detail

TypedResults.ValidationProblem(errorMessages) produces {Microsoft.AspNetCore.Http.HttpResults.ValidationProblem} with {Microsoft.AspNetCore.Http.HttpValidationProblemDetails} in detail.

I have my own IProblemDetailsWriter registered in DI before default one and when I use method on Results class it is hit. But when the TypedResults method is used my writer is not hit. In my code I'm using Results but I want to use MinimalApis.Extensions for input parameters validation with DataAnnotations. And there is used TypedResults.

using Microsoft.Extensions.DependencyInjection.Extensions;
using System.Net;

var builder = WebApplication.CreateBuilder(args);

builder.Services.TryAddEnumerable(ServiceDescriptor.Singleton<IProblemDetailsWriter, ValidationDetailsWriter>());
builder.Services.AddProblemDetails();

var app = builder.Build();

app.MapGet("results", () => { return Results.ValidationProblem(new Dictionary<string, string[]> { { "test", ["test"] } }); });
app.MapGet("typedresults", () => { return TypedResults.ValidationProblem(new Dictionary<string, string[]> { { "test", ["test"] } }); });

app.Run();

internal class ValidationDetailsWriter : IProblemDetailsWriter
{
  public bool CanWrite(ProblemDetailsContext context) => true;


  public async ValueTask WriteAsync(ProblemDetailsContext context)
  {
    context.HttpContext.Response.StatusCode = (int)HttpStatusCode.BadRequest;
    await context.HttpContext.Response.WriteAsync("My response");
  }
}

It looks like ProblemHttpResult is somewhere handled with ProblemDetailService but ValidationProblem not.

Is there a way how to handle ValidationProblem with same ProblemDetailService?

Thank you

[vernou]

When the result is of type that implement IResult, the response is generated by IResult.ExecuteAsync.

It's the case with ProblemHttpResult (that is returned by Results.ValidationProblem) and ValidationProblem (that is returned by TypedResults.ValidationProblem).

The method ProblemHttpResult.ExecuteAsync is :

public sealed class ProblemHttpResult : IResult, ...
{
    ...

    public async Task ExecuteAsync(HttpContext httpContext)
    {
        var problemDetailsService = httpContext.RequestServices.GetService<IProblemDetailsService>();
        if (problemDetailsService is null || !await problemDetailsService.TryWriteAsync(new() { HttpContext = httpContext, ProblemDetails = ProblemDetails }))
        {
            await HttpResultsHelper.WriteResultAsJsonAsync(
                httpContext,
                logger,
                value: ProblemDetails,
                ContentType);
        }
    }
}

The method ValidationProblem.ExecuteAsync is :

public sealed class ValidationProblem : IResult, ...
{
    public Task ExecuteAsync(HttpContext httpContext)
    {
        return HttpResultsHelper.WriteResultAsJsonAsync(
                httpContext,
                logger,
                value: ProblemDetails,
                ContentType);
    }
}

It's similar, just ProblemHttpResult allows you to inject a service to generate a custom response.

---

As hack, it's possible to add a operation filter to convert ValidationProblem to ProblemHttpResult :

app.MapGet("typedresults", () => { return TypedResults.ValidationProblem(new Dictionary<string, string[]> { { "test", ["test"] } }); })
    .AddEndpointFilter(async (efiContext, next) =>
    {
        var result = await next(efiContext);
        if(result is ValidationProblem vp)
        {
            return Results.Problem(vp.ProblemDetails);
        }
        return result;
    });

---

Can you specify your need?

[McMlok]

Thank you for the hint it works.

What I need? In our company we are using our own schema for ProblemDetail different than RFC. And if I use MinimalApis.Extensions WithParameterValidation extension method it returns response according to RFC because inside TypedResults.ValidationProblem method is used. I want to be able to use Results classes in an application and if we switch to RFC I only remove my own IProblemDetailsWriter implementation.

[vernou]

Indeed, WithParameterValidation return TypedResults.ValidationProblem on validation error.

If you just want modify the response body, maybe a custom JSON serializer can do the job.

[bjornen77]

There is an open issue and PR that will fix this:
#47631