.NET Core API 中的 CQS -- DI 配置不起作用

Question

I have implemented CQS pattern in my project. But i have created individual interfaces for each command handlers which is working. I'm trying to get it generated from one common interface (ICommandHandler) and when i try to configure it through DI in startup.cs the code is failing. The handlers are not initialized. Any help is appreciated.

The below is code

        public interface ICommand
    {
        Guid Id { get; }
    } 
 public abstract class Command : ICommand
    {
        public Guid Id { get; set; }
    
        protected Command()
        {
            Id = Guid.NewGuid();
    
        }

    }
  public class CreateAnnouncementDeliveryCommand : Command
    {
        public string DepliveryType { get; set; }
        public string Description { get; set; }
    }
  public interface ICommandHandler<in TCommand, TCommandResult> where TCommand : class, ICommand
    {
        Task<TCommandResult> Execute(TCommand command);
    }
 
 public partial class CreateAnnouncementDeliveryCommandHandler : ICommandHandler<CreateAnnouncementDeliveryCommand, CreateAnnouncementDeliveryCommand>
    {
        private readonly IAnnouncementDeliveryManager _manager;
        private readonly IMapper _mapper;

        public CreateAnnouncementDeliveryCommandHandler(IAnnouncementDeliveryManager manager, IMapper mapper)
        {
            _manager = manager;
            _mapper = mapper;
        }

        public Task<CreateAnnouncementDeliveryCommand> Execute(CreateAnnouncementDeliveryCommand command)
        {
          
           return not implemented
        }

    }

In Controller

public class AnnouncementDeliveryController : BaseController
    {
        private readonly ICreateAnnouncementDeliveryCommandHandler _createCommandHandler;
             private readonly IMapper _mapper;
        private readonly IHttpContextAccessor _httpContextAccessor;

        public AnnouncementDeliveryController(ICreateAnnouncementDeliveryCommandHandler createCommandhHndler,
                                       IMapper mapper,
                                       ILoggingService loggingService,
                                       IHttpContextAccessor httpContextAccessor,
                                       IUsersQueryHandler userQueryCommandHandler) : base(loggingService, userQueryCommandHandler, httpContextAccessor)
        {
            _createCommandHandler = createCommandhHndler;
           _httpContextAccessor = httpContextAccessor;
            _mapper = mapper;
        }
[HttpPost]
        [ActionName("AddAnnouncementDelivery")]
        public async Task<IActionResult> AddAnnouncementDelivery([FromBody] CreateAnnouncementDeliveryCommand _command)
        {
            try
            {
                var cmd = await _createCommandHandler.Execute(_command);
                return Ok(cmd);
            }
            catch (Exception e)
            {
                return BadRequest(e.Message);
            }
        }}

Adding the below in startup.cs :

services.AddTransient(typeof(ICommandHandler<CreateAnnouncementDeliveryCommand, CreateAnnouncementDeliveryCommand>), 
                      typeof(CreateAnnouncementDeliveryCommandHandler));

Answer 1

This is most likely a typo. Your configuration code registers ICommandHandler<CreateAnnouncementDeliveryCommand, CreateAnnouncementDeliveryCommand> while the container expects a ICreateAnnouncementDeliveryCommandHandler . None of the classes you posted implement ICreateAnnouncementDeliveryCommandHandler so I suspect the controller should expect a ICommandHandler<CreateAnnouncementDeliveryCommand, CreateAnnouncementDeliveryCommand> instead :

public class AnnouncementDeliveryController : BaseController
{
    private readonly ICommandHandler<CreateAnnouncementDeliveryCommand, CreateAnnouncementDeliveryCommand>
                    _createCommandHandler;

    public AnnouncementDeliveryController(
               ICommandHandler<CreateAnnouncementDeliveryCommand, CreateAnnouncementDeliveryCommand> createCommandhHndler,
               ....
   ) : base(loggingService, userQueryCommandHandler, httpContextAccessor)
   {
       _createCommandHandler = createCommandhHndler;
       ...
   }

This code is probably overengineered and too complex for whatever you want to do. Command-Query separation is a way to simplify complex domains, not add extra complexity. If the interfaces are so complex and so long that you miss such typos, you should probably rethink the design, and probably use less abstract types.