public class CreateItemCommand : Command
{    
    public CreateItemCommand(Guid id, string name) 
    {
        Id = id;
        Name = name;
    }
}

public class CreateItemCommandHandler : CommandHandler<CreateItemCommand>
{
    private readonly ItemRepository _repository;

    public CreateItemCommandHandler(ItemRepository repository)
    {
        _repository = repository;
    }

    public async Task Handle(CreateItemCommand command)
    {
        await _repository.Add(new Item(command.Id, command.Name));
    }
}

public class FindItemQuery : Query
{
    public Guid Id { get; private set; }

    public FindItemQuery(Guid id)
    {
        Id = id;
    }
}

public class FindItemQueryHandler : QueryHandler<FindItemQuery, ItemResponse>
{
    private readonly ItemRepository _repository;

    public FindItemQueryHandler(ItemRepository repository)
    {
        _repository = repository;
    }

    public async Task<ItemResponse> Handle(FindItemQuery query)
    {
        Item item = await _repository.GetById(query.Id);
        
        return new ItemResponse(item.Id, item.Name, item.IsCompleted);
    }
}

services.AddScoped<CommandHandler<CreateItemCommand>, CreateItemCommandHandler>();

services.AddScoped<QueryHandler<FindItemQuery, ItemResponse>, FindItemQueryHandler>();

services.AddCommandServices(typeof(Command).Assembly);
services.AddQueryServices(typeof(Query).Assembly);