Repository: dotnet/aspnetcore
File: src/Http/Routing/src/ValidationEndpointFilterFactory.cs (C#)

Code before:
                else
                {
                    validateContext.ValidationContext = validationContext;
                }

                await validatableParameter.ValidateAsync(argument, validateContext, context.HttpContext.RequestAborted);
            }

            if (validateContext is { ValidationErrors.Count: > 0 })
            {
                context.HttpContext.Response.StatusCode = StatusCodes.Status400BadRequest;

                var problemDetails = new HttpValidationProblemDetails(validateContext.ValidationErrors);

                var problemDetailsService = context.HttpContext.RequestServices.GetService<IProblemDetailsService>();
                if (problemDetailsService is not null)
                {
                    if (await problemDetailsService.TryWriteAsync(new()
                    {
                        HttpContext = context.HttpContext,
                        ProblemDetails = problemDetails
                    }))
                    {
                        // We need to prevent further execution, because the actual
                        // ProblemDetails response has already been written by ProblemDetailsService.
                        return await ValueTask.FromResult(EmptyHttpResult.Instance);
                    }
                }

                // Fallback to the default implementation.
                context.HttpContext.Response.ContentType = MediaTypeNames.Application.ProblemJson;
                return await ValueTask.FromResult(problemDetails);
            }

            return await next(context);
        };
    }

    private static bool IsServiceParameter(ParameterInfo parameterInfo, IServiceProviderIsService? isService)
        => HasFromServicesAttribute(parameterInfo) ||
           (isService?.IsService(parameterInfo.ParameterType) == true);

    private static bool HasFromServicesAttribute(ParameterInfo parameterInfo)
        => parameterInfo.CustomAttributes.OfType<IFromServiceMetadata>().Any();

    private static string GetDisplayName(ParameterInfo parameterInfo)
    {
        var displayAttribute = parameterInfo.GetCustomAttribute<DisplayAttribute>();
        if (displayAttribute != null)
        {
            return displayAttribute.Name ?? parameterInfo.Name!;

Review comment (suggestion):
```suggestion
                        return EmptyHttpResult.Instance;
```

Code after:
                else
                {
                    validateContext.ValidationContext = validationContext;
                }

                await validatableParameter.ValidateAsync(argument, validateContext, context.HttpContext.RequestAborted);
            }

            if (validateContext is { ValidationErrors.Count: > 0 })
            {
                context.HttpContext.Response.StatusCode = StatusCodes.Status400BadRequest;

                var problemDetails = new HttpValidationProblemDetails(validateContext.ValidationErrors);

                var problemDetailsService = context.HttpContext.RequestServices.GetService<IProblemDetailsService>();
                if (problemDetailsService is not null)
                {
                    if (await problemDetailsService.TryWriteAsync(new()
                    {
                        HttpContext = context.HttpContext,
                        ProblemDetails = problemDetails
                    }))
                    {
                        // We need to prevent further execution, because the actual
                        // ProblemDetails response has already been written by ProblemDetailsService.
                        return EmptyHttpResult.Instance;
                    }
                }

                // Fallback to the default implementation.
                context.HttpContext.Response.ContentType = MediaTypeNames.Application.ProblemJson;
                return problemDetails;
            }

            return await next(context);
        };
    }

    private static bool IsServiceParameter(ParameterInfo parameterInfo, IServiceProviderIsService? isService)
        => HasFromServicesAttribute(parameterInfo) ||
           (isService?.IsService(parameterInfo.ParameterType) == true);

    private static bool HasFromServicesAttribute(ParameterInfo parameterInfo)
        => parameterInfo.CustomAttributes.OfType<IFromServiceMetadata>().Any();

    private static string GetDisplayName(ParameterInfo parameterInfo)
    {
        var displayAttribute = parameterInfo.GetCustomAttribute<DisplayAttribute>();
        if (displayAttribute != null)
        {
            return displayAttribute.Name ?? parameterInfo.Name!;