I encounter issue in statement query able join between 2 tables, TblRequestTransfer and TblRequestTransferDetail.

My code:

using Api.Domain.Entity;
using Nest;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Api.App.Application.Query.Handler.RequestTransfer
{
    public class GetListItemIdRequestTransferQuery : IQueryBase<List<decimal>>
    {
        public decimal? id {get;set;}
    }

    public class GetListItemIdRequestTransferQueryHandler : IRequestBaseHandler<GetListItemIdRequestTransferQuery, List<decimal>>
    {
        public readonly IRepositoryService _repositoryService;
        public readonly IMapper _mapper;

        public GetListItemIdRequestTransferQueryHandler(IMapper mapper)
        {
            _repositoryService = EngineContext.Current.Resolve<IRepositoryService>(DataConnectionHelper.ConnectionStringNames.Pos)
                 ?? throw new ArgumentNullException(nameof(_repositoryService));
            _mapper = mapper ?? throw new ArgumentNullException(nameof(mapper));
        }

        public async Task<List<decimal>> Handle(GetListItemIdRequestTransferQuery request, CancellationToken cancellationToken)
        {
            if (request is null)
            {
                throw new BaseException("Yêu cầu không hợp lệ");
            }

            var query = await (from src in _repositoryService.Table<TblRequestTransfer>()
                               where src.Id == request.id
                               join detail in _repositoryService.Table<TblRequestTransferDetail>()
                               on src.Id equals detail.RequestId
                               select new
                               {
                                   detail.ItemId
                               })
                   .AsNoTracking()
                   .ToListAsync(cancellationToken);

            return query.Select(src => src.ItemId).ToList();
        }
    }
}

[issue 1] I try run and then input id of requestTranfer.

But counter equals 0

[issue 2] The method handler, which not successfully return value query, even though it’s default type list decimal? ItemId