ASP.NET 核心 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 核心 API，我正在尝试将 FluentValidation 与 Mediatr 结合使用。

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

Exception thrown: 'System.InvalidOperationException' in Microsoft.Extensions.DependencyInjection.dll: 'Unable to resolve service for type 'GetApplicationQuery' while attempting to activate 'GetApplicationQueryValidator'.'

查询、验证器和响应 class 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;
    }
}

我在启动 class 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);           
}

private static void AddMediatr(IServiceCollection services)
{
    const string applicationAssemblyName = "ApplicationApi";
    var assembly = AppDomain.CurrentDomain.Load(applicationAssemblyName);

    AssemblyScanner
        .FindValidatorsInAssembly(assembly)
        .ForEach(result => services.AddScoped(result.InterfaceType, result.ValidatorType));

    services.AddScoped(typeof(IPipelineBehavior<,>), typeof(ValidatorHandler<,>));

    services.AddMediatR(assembly);


}

我猜我的配置有误，但我已经多次更改配置但没有成功。

任何指导将不胜感激

Answer 1

GetApplicationQueryValidator 将 GetApplicationQuery 作为构造函数依赖项，但集合不知道它是否能够注入它。

也没有看到如何在该验证器中使用它。我建议从构造函数中删除 GetApplicationQuery，因为它看起来不需要。

public class GetApplicationQueryValidator : AbstractValidator<GetApplicationQuery> {
    public GetApplicationQueryValidator() { 
        RuleFor(m => m.Name).MinimumLength(30).WithMessage("Name must be greater than 30 characters, long");
    }
}

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

ASP.NET Core API, Mediatr send method raises exception unable to resolve service for type

c#

fluentvalidation

.net-core

mediatr

asp.net-core