C# 实体框架和 Linq 查询

Question

在下面的查询构建中，是否有任何理由Where子句B与Where子句A分开？

truckList = (from truck in _dbcontext.Truck.Where(x => x.ClientId == clientId) //(A)
    join comp in _dbcontext.TruckComponent
    on truck.Equipment.ProtId equals comp.ComponentId
    where truck.EquipmentId > 0 && truck.FieldId > 0 //B
    select NewTruckVmFromDbTruck(truck, comp)).AsEnumerable();

它们可以加入 A 或加入 B 吗？ 例如作为：

truckList = (from truck in _dbcontext.Truck.Where(
                x => x.ClientId == clientId && 
                truck.EquipmentId > 0 && 
                truck.FieldId > 0)
                ...rest of query...
             )

Answer 1

无论如何，最好不要混合 fluent 和 lambda 查询语法，怎么样：

truckList = (from truck in _dbcontext.Truck
             where truck.EquipmentId > 0 && truck.FieldId > 0 && truck.ClientId == clientId
             join comp in _dbcontext.TruckComponent on truck.Equipment.ProtId equals comp.ComponentId
             select NewTruckVmFromDbTruck(truck, comp)).AsEnumerable();

Answer 2

这是因为 'truck' 和 'comp' 来自不同的表

truckList = (from truck in _dbcontext.Truck.Where(x => x.ClientId == clientId) //(A)
join comp in _dbcontext.TruckComponent
on truck.Equipment.ProtId equals comp.ComponentId
where truck.EquipmentId > 0 && truck.FieldId > 0 //B
select NewTruckVmFromDbTruck(truck, comp)).AsEnumerable();

卡车来自名为“Truck”的表，而comp来自名为“TruckComponent”的表

两者都有不同的身份，如果你只选择' Truck '表，你不会得到' TruckComponent '表数据。

select NewTruckVmFromDbTruck(truck)).AsEnumerable();

希望这可以帮助