ASP NET Core在DbContext中使用异步介体

Question

我正在尝试通过依赖注入来访问dbContext。而且有效。

我正在启动时添加dbcontext

Services.AddDbContextPool<ApplicationDbContext>(options =>
            {
                options.UseMySql(Configuration["ConnectionStrings:DefaultConnection"],
                    b => b.MigrationsAssembly("Persistence"));
                options.UseOpenIddict();
            });

我也在中介中添加所有请求处理程序

services.AddMediatR(typeof(ChangePasswordRequestHandler).GetTypeInfo().Assembly);

我正在调解器的另一个请求中调用一个请求。这是一个示例

    public class CreateComment : IRequestHandler<CreateCommentRequestModel, ResponseViewModel>
    {
        private readonly ApplicationDbContext _context;
        private readonly IMediator _mediator;
        public CreateComment(ApplicationDbContext context, IMediator mediator)
        {
            _context = context;
            _mediator = mediator;
        }

        public async Task<ResponseViewModel> Handle(CreateCommentRequestModel request, CancellationToken cancellationToken)
        {
            _ = _mediator.Send(new SendCommentNotificationRequestModel(), CancellationToken.None);
            return new ResponseViewModel();
        }

这里是另一个请求处理程序

    public class SendCommentNotification : IRequestHandler<SendCommentNotificationRequestModel, ResponseViewModel>
    {
        private readonly ApplicationDbContext _context;
        private readonly IMediator _mediator;
        public SendCommentNotification(ApplicationDbContext context, IMediator mediator)
        {
            _context = context;
            _mediator = mediator;
        }

        public async Task<ResponseViewModel> Handle(SendCommentNotificationRequestModel request, CancellationToken cancellationToken)
        {
            await _mediator.Send(new SendNotificationToManyRequestModel(), CancellationToken.None);
            return new ResponseViewModel();
        }
    }

这是我的第三个处理程序

    public class SendNotificationToMany : IRequestHandler<SendNotificationToManyRequestModel, ResponseViewModel>
    {
        private readonly ApplicationDbContext _context;
        private readonly INotificationService _notificationService;
        public SendNotificationToMany(
            INotificationService notificationService, ApplicationDbContext context)
        {
            _notificationService = notificationService;
            _context = context;
        }

        public async Task<ResponseViewModel> Handle(SendNotificationToManyRequestModel request,
            CancellationToken cancellationToken)
        {
           //DbContext is disposed hence not usable when accessed here.

            return new ResponseViewModel();
        }
    }

问题是在第三个Handler上工作时DbContext被处置了。我该怎么解决？

如果在第一个处理程序上添加await，则它应能正常工作，但我不想等待，我希望它在后台运行。

我知道修复程序很小，但是我无法弄清楚。

Answer 1

Kestrel在请求的生存期内创建一个服务范围。合并范围完成后，将处理所有IDisposable服务。

Answer 2

我认为错误位于此处：