Mediatr如何接线？

Question

更新：

项目中的Mediatr用于分发消息时没有任何自定义逻辑。我可以说它用作事件聚合器吗？

---

在https://github.com/JasonGT/NorthwindTraders的源代码中，控制器从ControllerBase获取调解器。

[ApiController]
[Route("api/[controller]/[action]")]
public abstract class BaseController : ControllerBase
{
    private IMediator _mediator;

    protected IMediator Mediator => _mediator ??= HttpContext.RequestServices.GetService<IMediator>();
}

在控制器中，它调用Mediator.Send(...)将消息发送到调解器。

public class EmployeesController : BaseController
{
    // ....
    [HttpGet("{id}")]
    [ProducesResponseType(StatusCodes.Status200OK)]
    public async Task<ActionResult<EmployeeDetailVm>> Get(int id)
    {
        return Ok(await Mediator.Send(new GetEmployeeDetailQuery { Id = id }));
    }

并且内部类Handle()中的方法GetEmployeeDetailQuery.GetEmployeeDetailQueryHandler将被查询消息GetEmployeeDetailQuery调用。如何接线？

public class GetEmployeeDetailQuery : IRequest<EmployeeDetailVm>
{
    public int Id { get; set; }

    public class GetEmployeeDetailQueryHandler : IRequestHandler<GetEmployeeDetailQuery, EmployeeDetailVm>
    {
        private readonly INorthwindDbContext _context;
        private readonly IMapper _mapper;

        public GetEmployeeDetailQueryHandler(INorthwindDbContext context, IMapper mapper)
        {
            _context = context;
            _mapper = mapper;
        }

        public async Task<EmployeeDetailVm> Handle(GetEmployeeDetailQuery request, CancellationToken cancellationToken)
        {
            var vm = await _context.Employees
                .Where(e => e.EmployeeId == request.Id)
                .ProjectTo<EmployeeDetailVm>(_mapper.ConfigurationProvider)
                .SingleOrDefaultAsync(cancellationToken);

            return vm;
        }
    }
}

Answer 1