How to show (AddProblemDetails) multiple validation error against single property using Fluent Validation & MediatR Pipeline Behaviour

[akbarbd]

 x.Map<ValidationException>(ex => new ProblemDetails
        {
            Title = "input validation rules broken",
            Status = (int)ex.StatusCode,
            Detail = ex.Message,
            Type = "https://somedomain/input-validation-rules-error"
        });

[khellang]

Hi @akbarbd! 👋

See https://github.com/khellang/Middleware/blob/master/samples/ProblemDetails.Sample/ProblemDetailsOptionsExtensions.cs

[akbarbd]

I am develop this way but multiple error is not showing and output is unreadable exception.

1 . Exception Inheritance Class

 public class ValidationException : Exception
{
    public IDictionary<string, string[]> Errors { get; } 
    public ValidationException(string message, int? code = null) : base(message, code: code)
    {
        Errors = new Dictionary<string, string[]>();
    }

    public ValidationException(IEnumerable<ValidationFailure> failures):this("One or more validation failures have occurred.")
    {
        Errors = failures
            .GroupBy(e => e.PropertyName, e => e.ErrorMessage)
            .ToDictionary(failureGroup => failureGroup.Key, failureGroup => failureGroup.ToArray());
    }
}

2. MediatR Pipeline Behavior

 public sealed class ValidationBehavior<TRequest, TResponse> : IPipelineBehavior<TRequest, TResponse>
   where TRequest : class, IRequest<TResponse>
  {
      private readonly IEnumerable<IValidator<TRequest>> _validators;
      private readonly IServiceProvider _serviceProvider;

      public ValidationBehavior(IServiceProvider serviceProvider, IEnumerable<IValidator<TRequest>> validators)
      {
          _serviceProvider = serviceProvider;
          _validators = validators;
      }
      public async Task<TResponse> Handle(TRequest request, CancellationToken cancellationToken, RequestHandlerDelegate<TResponse> next)
      {
          if (_validators.Any())
          {
              var context = new ValidationContext<TRequest>(request);

              var validationResults = await Task.WhenAll(
                  _validators.Select(v =>
                      v.ValidateAsync(context, cancellationToken)));

              var failures = validationResults
                  .Where(r => r.Errors.Any())
                  .SelectMany(r => r.Errors)
                  .ToList();

              if (failures.Any())
                  throw new ValidationException(failures);
          }
          return await next();
      }
  }

3. ProblemDetailsExtensions

     public static IServiceCollection AddCustomProblemDetails(this IServiceCollection services)
      {
          services.AddProblemDetails(x =>
          {
               x.IncludeExceptionDetails = (ctx, _) =>
              {
                  // Fetch services from HttpContext.RequestServices
                  var env = ctx.RequestServices.GetRequiredService<IHostEnvironment>();
                  return env.IsDevelopment() || env.IsStaging();
              };
           
            // Exception will produce and returns from  FluentValidation RequestValidationBehavior
            x.Map<ValidationException>(ex => new ProblemDetailsWithCode
            {
                Title = "input validation rules broken",
                Status = (int)ex.StatusCode,
                Detail = ex.Message,
                Type = "https://somedomain/input-validation-rules-error", 
            });
          
        });
        return services;
    }

4. Startup
builder.Services.AddCustomProblemDetails();
app.UseProblemDetails();

[khellang]

I am develop this way but multiple error is not showing

I don't see you pulling out the Errors from the ValidationException and mapping it onto the ProblemDetailsWithCode class anywhere?

and output is unreadable exception

If you want to turn off the exception details, you just need to return false from your IncludeExceptionDetails hook.