Question

在下面的LinQ查询中获取电话号码时，我正在调用另一个异步方法GetAspNetUserPhoneNumberByAccountId，它将引发此错误

错误CS4034'await'运算符只能在异步lambda表达式内使用。考虑使用'async'修饰符标记此lambda表达式。

有人知道吗？

 var fullAppointment = await Task.Run(() => Context.AppointmentDetail
     .Where(u =>
     u.StartDateTime >= startdatetime
      && u.EndDateTime <= enddatetime

      )
       .Select(x => new Contracts.CalenderModel2()
        {
          StatusId = (Contracts.Enum.EnumWOStatus)x.Status,
          FName = x.Appointment != null ? x.Appointment.Customer.Account.FName : "",
          LName = x.Appointment != null ? x.Appointment.Customer.Account.LName : "",
          **PrimaryPhone = x.Appointment != null ?
          (await _userRepository.GetAspNetUserPhoneNumberByAccountId( x.Appointment.Customer.AccountId))**
          : "",
          Year = x.Appointment != null && x.Appointment.Vehicle != null ? x.Appointment.Vehicle.MakeYear.Year : 0,
          Make = x.Appointment != null && x.Appointment.Vehicle != null ? x.Appointment.Vehicle.VehicleMaker.MakerName : "",
          Model = x.Appointment != null && x.Appointment.Vehicle != null ? x.Appointment.Vehicle.VehicleModel.Model : "",
          AppointmentId = x.AppointmentId,
          JobEndDateTime = x.EndDateTime,
          JobStartDateTime = x.StartDateTime,
          ColorCategory = x.AppointmentType.ColorCategory,

          SalesRepersentativeUserId =
(x.Appointment != null && x.Appointment.Customer.CustomerBillTo.Count > 0)
              ? x.Appointment.Customer.CustomerBillTo.FirstOrDefault().BillToId : Guid.Empty,

          FullAppointmentDetail = new Contracts.FullAppointmentDetail
          {
            BayId = x.BayId,
            BayName = x.WorkArea != null ? x.WorkArea.BayName : "",
            WorkTypeId = x.WorkTypeId,
            WorkTypeName = x.WorkType != null ? x.WorkType.WorkTypeName : "",
            JobId = x.Appointment != null && x.Appointment.Job != null ? x.Appointment.Job.Id : Guid.Empty,
            JobIdInt = x.Appointment != null && x.Appointment.Job != null ? x.Appointment.Job.JobIdInt : 0,
            AssigneeUserId = x.AssigneeUserId,
            WorkOrderId = x.WorkOrders.FirstOrDefault() != null ? x.WorkOrders.FirstOrDefault().Id : Guid.Empty
          }

        })
        .ToList());

GetAspNetUserPhoneNumberByAccountId的定义在下面给出

public async Task<string> GetAspNetUserPhoneNumberByAccountId(Guid accountId)
{
  var phone = await Task.Run(() => _Context.Account.Where(ac => ac.Id.Equals(accountId))
   .Join(_Context.AspNetUsers, ac => ac.AspNetUserId, u => u.Id, (ac, u) => new 
   {
     PhoneNumber = u.PhoneNumber,

   }).FirstOrDefault());

  return phone!=null?phone.ToString():"";
}

Answer 1

我同意您在注释中不需要使用异步方法的意见。另外，该查询将不会优化。对于条件条件中的每个项目，您都将查询到数据库。如果您有大量数据，DB的性能将下降。我认为在这种情况下最好对数据库执行2次查询。用于获取AppointmentDetail和用于获取所有帐户的另一个查询。并且两个查询都带有异步调用。然后将其组合到您的Contracts.CalenderModel2类中。

它将更具可读性并且工作更快。而且不要使用Task.Run（）;

“ await”运算符只能在异步lambda表达式中使用。考虑使用'async'修饰符标记此lambda表达式

1 个答案: