LINQ - 'join子句中某个表达式的类型不正确'

Question

我有一个复杂的LINQ to SQL查询，它连接到两个表 - 一个很简单，工作正常，但一个相当复杂，我得到The type of one of the expressions in the join clause is incorrect. Type inference failed in the call to 'GroupJoin

这是一个相当长的查询，我在一个有互联网访问权限的工作上进行开发，所以我想我会看看这个问题似乎就足够了：

join consignments in dc.Consignments
    .FirstOrDefault(x => x.TripDate > dateFrom 
    && x.TripDate < dateTo 
    && x.DeliveryDepot == depot.Letter 
    && (x.DeliveryStatus == 2 || x.DeliveryStatus == 3))
  on new { Reg = s.VehicleReg, Depot = s.VehicleDepot } 
      equals new { Reg = consignments.VehicleReg, Depot = consignments.DeliveryDepot }
  into con

我确保数据类型相同，但仍然无法正常工作。有什么想法吗？

Answer 1

您确定s.VehiculeDepot与consignments.DeliveryDepot的类型相同吗？

on new { Reg = s.VehicleReg, Depot = s.VehicleDepot } 
equals new { Reg = consignments.VehicleReg, Depot = consignments.DeliveryDepot }

Answer 2

我认为问题出在这一部分：

on new { Reg = s.VehicleReg, Depot = s.VehicleDepot }
   equals
   new { Reg = consignments.VehicleReg, Depot = consignments.DeliveryDepot }

确保s.VehicleReg与consignments.VehicleReg的类型相同，s.VehicleDepot的类型与consignments.DeliveryDepot相同。

Answer 3

还要确保您的成员名称完全相同且相同。例如：

 new { Reg = s.VehicleReg, Depot = s.VehicleDepot }
   equals
   new { Reg = consignments.VehicleReg, DEpot = consignments.DeliveryDepot }

会失败，因为在第二个匿名类型中，depot是不同的情况。