尝试将 IPipelineBehavior 与 ASP.NET 核心一起使用 - 得到 System.InvalidCastException

Question

我正在使用 Mediatr 3 的管道行为新功能。问题是，当我将它们连接到 Mediatr 时，每次 .Send() 调用都会抛出异常 (System.InvalidCastException)。处理程序被调用得很好，但是当调用管道行为时，它失败了。

这是我的设置：

    services.AddScoped<SingleInstanceFactory>(p => t => p.GetRequiredService(t));
    services.AddScoped<MultiInstanceFactory>(p => t => GetRequiredServices(p,t));
    services.AddScoped(typeof( IPipelineBehavior<, >), typeof(AddSessionBehavior<, >));
    services.AddMediatR();

我的行为：

public class AddSessionBehavior<TRequest, TResponse> : IPipelineBehavior<TRequest, TResponse>
    {
        IHttpContextAccessor Accessor;
        public AddSessionBehavior(IHttpContextAccessor anAccessor)
        {
            this.Accessor = anAccessor;
        }
        public async Task<TResponse> Handle(TRequest request, RequestHandlerDelegate<TResponse> next)
        {

            var response = await next();
            return response;

        }
    }

当我通过中介发送第一条消息时，我得到：

System.InvalidCastException occurred
  HResult=0x80004002
  Message=Object cannot be stored in an array of this type.
  Source=<Cannot evaluate the exception source>
  StackTrace:
   at System.Array.InternalSetValue(Void* target, Object value)
   at System.Array.SetValue(Object value, Int32[] indices)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitClosedIEnumerable(ClosedIEnumerableCallSite closedIEnumerableCallSite, ServiceProvider provider)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitTransient(TransientCallSite transientCallSite, ServiceProvider provider)
   at Microsoft.Extensions.DependencyInjection.ServiceProvider.<>c__DisplayClass16_0.<RealizeService>b__0(ServiceProvider provider)
   at Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions.GetRequiredService(IServiceProvider provider, Type serviceType)
   at MediatR.ServiceCollectionExtensions.GetRequiredServices(IServiceProvider provider, Type serviceType)
   at MediatR.Internal.RequestHandlerImpl`2.GetPipeline(TRequest request, RequestHandlerDelegate`1 invokeHandler, MultiInstanceFactory factory)
   at MediatR.Internal.RequestHandlerImpl`2.Handle(IRequest`1 request, CancellationToken cancellationToken, SingleInstanceFactory singleFactory, MultiInstanceFactory multiFactory)
   at MediatR.Mediator.Send[TResponse](IRequest`1 request, CancellationToken cancellationToken)
   at Merlin.Web.Controllers.CourseController.Add(CourseAddVM model)

如果我注释掉我的行为的连接，我的处理程序就会被调用。应用程序的其余部分似乎可以正常工作。

我做错了什么？

Answer 1

我想通了。

原来在我的应用程序的不同名称空间中创建了一个与我的行为同名的内部 class。可能是 "Generate Class definition" 的结果。

删除生成的 class 解决了问题。

尝试将 IPipelineBehavior 与 ASP.NET 核心一起使用 - 得到 System.InvalidCastException

Trying to use IPipelineBehavior with ASP.NET Core - get System.InvalidCastException

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