Question

我之前提出过类似的问题。我有一个结构如下的车型列表：

class Car
    {
        public string Make { get; set; }
        public string Model { get; set; }
        public string SecondHand { get; set; }
        public int AccidentCount { get; set; }
        public int MaintenanceCount { get; set; }
    }

List<Car> cars = new List<Car>()
{
new Car(){Make = "Mercedes", Model = "E-200", SecondHand ="N", AccidentCount = 1 ,MaintenanceCount = 0},
new Car(){Make = "Mercedes", Model = "E-200", SecondHand ="N", AccidentCount = 1 ,MaintenanceCount = 1},
new Car(){Make = "Mercedes", Model = "E-200", SecondHand ="Y", AccidentCount = 1 ,MaintenanceCount = 1},
new Car(){Make = "Mercedes", Model = "E-180", SecondHand ="N", AccidentCount = 0 ,MaintenanceCount = 1},
new Car(){Make = "Mercedes", Model = "E-180", SecondHand ="N", AccidentCount = 1 ,MaintenanceCount = 1} 
};

我在查询输出中需要的是Make和Model的2列，通过对它们进行分组，得到2列中的AccidentCount和MaintenanceCount的总和，最后如果给定模型输出“Y”有任何“SecondHand”值“Y” “否则”N“。

上面的输出应该是：

Make      Model  AccidentCount  MaintenanceCount SecondHand  
Mercedes  E-200  3              2                Y 
Mercedes  E-180  1              2                N

Answer 1

我在查询输出中需要的是通过对它们进行分组的2列Make和Model，

cars.GroupBy(c=> new {c.Make,c.Model})

获取2列
中的AccidentCount和MaintenanceCount之和

AccidentCount = g.Sum(c=>c.AccidentCount),
MaintenanceCount = g.Sum(c=>c.MaintenanceCount)

最后如果有任何＆＃34; SecondHand＆＃34;值＆＃34; Y＆＃34;对于给定的模型输出＆＃34; Y＆＃34;否则＆＃34; N＆＃34;。

SecondHand = g.Any(c=> c.SecondHand=="Y") ? "Y" : "N"

最终查询如下所示：

cars.GroupBy(c=> new {c.Make,c.Model})
        .Select(g=> new Car {
              Make = g.Key.Make,
              Model = g.Key.Model, 
              AccidentCount = g.Sum(c=>c.AccidentCount),
              MaintenanceCount = g.Sum(c=>c.MaintenanceCount),
              SecondHand = g.Any(c=> c.SecondHand=="Y") ? "Y" : "N"
              });

具有分组和条件结果的linq查询

1 个答案: