ASP.NET Core API，Mediatr 发送方法引发无法解析类型服务的异常

Question

我有一个 ASP.NET Core API，我正在尝试将 FluentValidation 与 Mediatr 一起使用。

当前，当控制器方法尝试在它生成的 mediatr 实例上调用 Send 时：

抛出的异常：Microsoft.Extensions.DependencyInjection.dll 中的“System.InvalidOperationException”：“尝试激活‘GetApplicationQueryValidator’时无法解析‘GetApplicationQuery’类型的服务。”

查询、验证器和响应类如下所示：

public class GetApplicationQuery : IRequest<Response>

{

    private string _name;

    public GetApplicationQuery(string name)

    {

        _name = name;

    }

    public string Name { get { return _name; } }

}

public class GetApplicationQueryHandler : IRequestHandler<GetApplicationQuery, Response>

{

    public GetApplicationQueryHandler() { }

    public async Task<Response> Handle(GetApplicationQuery request, CancellationToken cancellationToken)

    {

        return new Response("yadda yadda");            

    }

}

public class GetApplicationQueryValidator : AbstractValidator<GetApplicationQuery>

{

    public GetApplicationQueryValidator(GetApplicationQuery request)

    {   

        RuleFor(m => m.Name).MinimumLength(30).WithMessage("Name must be greater than 30 characters, long");

    }

}

public class Response

{

    private readonly IList<string> _messages = new List<string>();

    public IEnumerable<string> Errors { get; }

    public object Result { get; }

    public Response() => Errors = new ReadOnlyCollection<string>(_messages);

    public Response(object result) : this() => Result = result;

    public Response AddError(string message)

    {

        _messages.Add(message);

        return this;

    }

}

我在 Startup 类中的配置如下所示：

public void ConfigureServices(IServiceCollection services)

{

    AddMediatr(services);

    services.AddMvc().AddFluentValidation(fv => 

        {

            fv.RegisterValidatorsFromAssemblyContaining<Startup>();

            fv.RunDefaultMvcValidationAfterFluentValidationExecutes = false;

        }).SetCompatibilityVersion(CompatibilityVersion.Version_2_2);           

}

Answer 1

GetApplicationQueryValidator正在GetApplicationQuery作为构造函数依赖项，但集合不知道它是否能够注入它。也没有看到它是如何在该验证器中使用的。我建议GetApplicationQuery从构造函数中删除，因为它看起来并不需要。public class GetApplicationQueryValidator : AbstractValidator<GetApplicationQuery> {&nbsp; &nbsp; public GetApplicationQueryValidator() {&nbsp;&nbsp; &nbsp; &nbsp; &nbsp; RuleFor(m => m.Name).MinimumLength(30).WithMessage("Name must be greater than 30 characters, long");&nbsp; &nbsp; }}