c# - 在 MediatR 管道行为中返回错误的响应

Question

我是 MediatR 的新手，尝试使用管道行为进行请求验证，如果发生任何错误，我遇到的所有示例都会抛出 ValidationException。
以下代码是验证管道的示例：

public class ValidationPipeline<TRequest, TResponse> : IPipelineBehavior<TRequest, TResponse>
where TRequest : IRequest<TResponse>
{
    private readonly IEnumerable<IValidator> _validators;

    public ValidationPipeline(IEnumerable<IValidator<TRequest>> validators)
    {
        _validators = validators;
    }

    public Task<TResponse> Handle(TRequest request, CancellationToken cancellationToken, RequestHandlerDelegate<TResponse> next)
    {
        var context = new ValidationContext<TRequest>(request);
        var validationFailures = _validators
            .Select(validator => validator.Validate(context))
            .SelectMany(validationResult => validationResult.Errors)
            .Where(validationFailure => validationFailure != null)
            .ToList();

        if (validationFailures.Any())
        {
            throw new FluentValidation.ValidationException(validationFailures);
        }
        
        return next();
    }
}

此方法工作正常，但我想返回带有验证错误的响应（不）抛出异常，所以我尝试了这个：

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

    public ValidationBehavior(IEnumerable<IValidator<TRequest>> validators)
    {
        _validators = validators;
    }

    public Task<BaseResponse<TResponse>> Handle(TRequest request, CancellationToken cancellationToken, RequestHandlerDelegate<BaseResponse<TResponse>> next)
    {
        var context = new ValidationContext<TRequest>(request);
        var validationFailures = _validators
            .Select(validator => validator.Validate(context))
            .SelectMany(validationResult => validationResult.Errors)
            .Where(validationFailure => validationFailure != null)
            .ToList();

        if (validationFailures.Any())
        {
            return Task.FromResult(new BaseResponse<TResponse>
            {
                Code = 400,
                Message = "Validation error",
                Error = validationFailures.Select(err => err.ErrorMessage)
            });
        }
        else
        {
            return next();
        }
    }

但现在验证管道代码不执行，
并且执行转到常规处理程序（例如：注册用户处理程序）。

我的回应（在所有处理程序中使用）：

public class BaseResponse<TResponse>
{
    public int Code { get; set; }
    public string Message { get; set; }
    public TResponse Result { get; set; }
    public object Error { get; set; }
    public string TraceIdentifier { get; set; }
}

像这样使用 DI 注册行为：

services.AddTransient(typeof(IPipelineBehavior<,>), typeof(ValidationBehavior<,>));

任何帮助将不胜感激。

标签： c#asp.net-coremediatr